Drawing up tasks of the form "Choice of 2 true statements out of 5 possible"
Physics teacher Vlasova N.N.
Traditionally, collections of preparation for the exam contain calculation tasks of different levels of complexity, while among the tasks of KIM there are tasks with a choice of two correct statements out of five proposed. Tasks are often more difficult than ordinary tasks, because require students to be able to operate with a large block of theoretical knowledge, to analyze laws and dependencies, to establish analytical and logical functional dependencies. There are practically no manuals and collections of problems with such formulations.
Based on the database of USE tasks, I tried to compose such tasks in kinematics myself, changing the wording. This is the transformation technology. The traditionally formulated problem is solved as completely as possible, according to the solution and according to the results of the solution, true and false statements are formulated.
Example 1 Traditional Formulation
The material point moves uniformly accelerated along the OX axis so that the dependence of the coordinate on time is represented by a table. Determine the acceleration of the movement. (Question options: determine the initial speed; determine the displacement in 5 s; what will be the speed at time 4 s?)
| t,s | |||
| hm |
Example 1: Changed wording
The material point moves along the axis so that the dependence of the coordinate on time is represented by a table. Choose two true statements.
| t,s | |||
| hm |
1. The material point makes a uniform movement.
2. The initial speed of the body is zero.
3.Modulus of acceleration of a material point is equal to 1m/ With2 .
4. At time 4 s, the coordinate of the material point is 11 m.
5. At the moment of time 5 s, the modulus of the body's velocity is 5.5m/ With.
Solution
The material point at the initial moment is at the origin, but it does not follow from this that the movement begins from a state of rest.
The change in coordinate for the first second was 1 m. If the movement was uniform, then for the next two seconds the change in coordinate should be 2 m, and from the table it is 5 m.
Let us assume that the motion is uniformly accelerated. In the formula for the dependence of the coordinate on time, we substitute the values from the table, compose a system of two equations, solving which, we obtain the projections of the initial velocity and acceleration.
Substituting the time 4 s into the coordinate formula, and the time 5 s into the velocity projection formula, we obtain the values of the quantities.
Correct answers: 3; 5.
Example 2 Traditional Formulation
The material point moves 5 s in the plane so that X = - 9 + 4t and Y = 4t - t2 . Calculate the body's velocity and acceleration 2 s after the start of motion.
Example 2: Changed wording
The material point moves 5 s so that X = - 9 + 4t and Y = 4t - t2 . Choose two true statements.
1. The trajectory of the body is a straight line.
2. The module of the initial speed is 5m/ With.
3.Modulus of acceleration after 2 s is 2m/ With2 .
4. After 4 seconds, the body stops.
5. The coordinate Y takes on the maximum value at the time t = 2 s.
Solution
We use the Cartesian coordinate system. The X coordinate changes linearly, the Y coordinate changes quadratically, therefore, the dependence Y (x) will be represented by a parabola, the branches of which are directed downwards. The material point does not move in a straight line.
From the analysis of the dependences of coordinates on time, it follows that the projection of the initial velocity on the OX axis is equal to "+4m/ With” and on the y-axis is “-4m/ With". By the Pythagorean theorem, we calculate the module of the initial speed.
From the analysis of the dependences of coordinates on time, it follows that the projection of acceleration on the OX axis is "0" and on the OY axis is "-2m/ With2 ". By the Pythagorean theorem, we calculate the acceleration module, it does not change.
If the body must stop, then both projections of its velocity on the axis must be zero, and the projection of velocity on the OX axis is constant and not zero.
If the value has a maximum value, then the graph of the function has an inflection point and the derivative of the function is equal to zero.
Correct answers: 3; 5.
Addition: the traditional wording allows you to turn the problem into an Olympiad, if the question for it is formulated as follows: “1) draw a graph of Y(x) for 5 seconds of movement; 2) at what point in time is the velocity vector perpendicular to the acceleration vector?
Example 3 Traditional Formulation
The movement of a material point is described by the dependencies Х = 0.05cos2t and Y= 0.05sin2t. Calculate the speed of movement. (Question option: Calculate the acceleration.)
Example 3: Changed wording
The movement of a material point is described by the dependencies Х = 0.05cos2t and Y= 0.05sin2t. Choose two true statements.
1. The trajectory of the body is a sinusoid.
2.Modulus of body speed is 0.1m/ With.
3. The acceleration of the body is zero.
4. A material point moves along a circle with a radius of 5 cm.
5. After 1 s after the start of movement, the displacement of a material point is 0.1 m.
Solution
We use the Cartesian coordinate system. The X and Y coordinates of a material point change according to the trigonometric law. The trajectory cannot be a sinusoid.
Please note that before the cos and sin functions, the coefficient is the same and the argument of the functions is the same. We square X and Y and add them. The transformation of the expression leads to the circle formula.
The velocity projection shows the rate of change of the coordinate, therefore, we take the time derivative of the dependence of the coordinates on time. We get that the velocity projections on the axis also change according to the trigonometric law. The velocity modulus can be calculated using the Pythagorean theorem. In the transformations, we also use the basic trigonometric identity.
The projection of acceleration shows the rate of change of speed, therefore, from the dependences of the projections of speed on time, we take the derivative with respect to time. We get that the acceleration projections on the axis also change according to the trigonometric law. Modulus cannot be null.
Analyzing the argument "2t", we find that the period is 3.14 s. In 1.57 s, the material point will pass half of the circle and its displacement will be equal to the diameter, i.e. 0.1 m
Correct answers: 2; four.
Example 4 Traditional Formulation
For a material particle whose initial coordinate is zero, the graphs of velocity projections are given. Calculate the path traveled by the particle in 2 s.
Example 4: Changed wording
For a material particle whose initial coordinate is zero, the graphs of velocity projections are given. Choose two true statements.
1. During the entire movement, the acceleration of the body is zero.
2. The movement of the body along the OS axis was 1.5 m.
3. The body reached its maximum speed 1 s after the start of movement.
4. The distance traveled in 2 s was 2.5 m.
5. The trajectory of the body is a parabola.
Solution
It follows from the first graph that only for the first second the particle moved uniformly in the direction of the OX axis, then there is no movement along the OX axis. It follows from the second graph that the particle moved uniformly accelerated against the OS axis for 1 s and uniformly for another 1 s in the same direction. Consequently, part of the time the particle moved with acceleration.
We use the Cartesian coordinate system. In the first second of motion, the trajectory was a branch of a parabola, branches down on the coordinate plane. In the second second, the trajectory was a straight line segment parallel to the OS axis.
Using the dependence "the area of the figure under the velocity projection graph is numerically equal to the displacement projection", we calculate the displacement along the y-axis.
The maximum speed is calculated by the Pythagorean theorem, using the modules of the maximum projections of the velocity vector on the axis.
Correct answers: 2; 3.
Conclusion
Compiling tasks for the KIM USE of the type “Choice of 2 true statements out of 5 possible” (such tasks are also included in the materials of the OGE-9) is a rather laborious and creative process that requires a new look at solving and designing tasks. Again, none of the collections offers such tasks. I hope that my modest experience in developing such assignments will be useful to physics teachers.
The test work includes 18 tasks. To complete the work in physics, 1 hour 30 minutes (90 minutes) is allotted.
Read the list of concepts that you encountered in the course of physics.
Magnetic induction vector, meter, surface area, volt, speed, second.
Divide these concepts into two groups according to your chosen attribute. Write in the table the name of each group and the concepts included in this group.
Choose two true statements about physical quantities or concepts. Circle their numbers.
1. The earth acts on the ball with a gravitational force F 1 . The gravitational force F 2 with which the ball acts on the Earth is less than F 1
2. In a closed system of bodies, the total energy does not change with any interactions within this system of bodies.
3. The frame of reference associated with the aircraft is inertial if the aircraft makes a "dead loop".
4. Electromagnetic induction - the phenomenon of the occurrence of an electric current in a closed circuit when the magnetic flux passing through it changes.
5. In mechanical motion, force and speed always coincide in direction.
Show answer
The astronaut is in space. What is the name of the state in which the astronaut is?
Show answer
weightlessness
Read the text and fill in the missing words:
decreases
increases
does not change
Words in the answer may be repeated.
When a gun is fired, the bullet and the gun begin to move in opposite directions at different speeds. In this case, the bullet momentum module is _______. The momentum modulus of a shotgun is _______. The total momentum of the gun-bullet system is ________ and is equal to 0.
Show answer
increases, increases, does not change
An ideal gas receives an amount of heat of 400 J from an external source and does work of 500 J. By how much will the module of the internal energy of the gas change?
Show answer
\alpha, \beta, \gamma radiations are placed in an electric field, between two charged plates A and B. Which particle stream is a radiation?
Show answer
helium atom nucleus
The figures show the emission spectra of atomic vapors of hydrogen (1), helium (2), sodium (3), an unknown sample (4) Does the sample contain hydrogen, helium and sodium? Explain the answer.
Show answer
Contains hydrogen, helium and sodium
A straight conductor 2 m long, through which an electric current of 3 A flows, enters a uniform magnetic field, the lines of force of which are perpendicular to the conductor. A force of 1 mN begins to act on the conductor from the side of the magnetic field. Calculate the magnitude of the magnetic field induction. Write formulas and do calculations.
Show answer
Possible answer
The Ampere force is determined by the formula F a = BLI.
Hence B \u003d F a /LI \u003d 0.001 N / (2 m 3 A) ≈ 1.6 10 -4 T.
Arrange the types of electromagnetic waves emitted by the Sun in ascending order of their wavelength. Write down the corresponding sequence of numbers in your answer.
1) ultraviolet radiation
2) thermal radiation
3) visible light
Answer: _____ → _____ → _____
Show answer
The atmospheric pressure was measured using a barometer. The upper scale of the barometer is graduated in mm Hg. Art., and the lower scale is in hPa (see figure). The error in pressure measurements is equal to the division value of the barometer scale.
Answer: _________ mmHg. Art.
Show answer
745 ± 1 mmHg Art.
The student studied the dependence of voltage on charge and, using the well-known formula C \u003d Q / U, decided to calculate the capacitance of a capacitor. What number did he get, taking into account the measurement errors of q and U, respectively, equal to 0.05 μ C and 0.25 kV. What is the approximate free fall acceleration on the planet?
Show answer
You need to investigate the dependence of the period of free oscillations of a spring pendulum on the stiffness of the spring. The following equipment is available:
Tripod with foot;
A set of springs of different stiffness;
A set of cargoes;
Stopwatch.
Describe the procedure for conducting the study.
In response:
1. Draw or describe the experimental setup.
2. Describe the procedure for conducting research.
Show answer
Possible answer
1. The setup shown in the picture is used: spring, one weight and a stopwatch.
2. One load is suspended from the spring and the time of 10 oscillations is measured. The resulting time is divided by the number of oscillations, and the period is obtained.
3. Without changing the number of weights, a spring of a different stiffness is taken and the period measurements are repeated. Similar measurements can be made with a third spring.
4. The obtained values of the periods are compared.
Establish a correspondence between the examples and the physical phenomena that these examples illustrate. For each example of the manifestation of physical phenomena from the first column, select the appropriate name of the physical phenomenon from the second column.
A) The period of revolution of an artificial satellite around the Earth increases as its orbit increases.
B) When turning the car on a level road, all passengers deviate to the outside of the road.
PHYSICAL PHENOMENA
1) The period of revolution of the body depends on the distance to the center of the circle.
2) The period of revolution of the satellite does not depend on the mass of the satellite.
3) When moving in a circle, the body has a centripetal acceleration.
Show answer
Read the text and do tasks 14 and 15.
How a solar sail works
The solar sail was invented by the Russian scientist Friedrich Arturovich Zander (1887-1933). He was the first to put forward ideas about the structure and principles of using a solar sail as a propulsion device for space flights. He described the most optimal option in the article "Flights to other planets" in 1924.
For the first time, a thorough and complete study of the pressure of light on solid bodies was carried out by Pyotr Nikolaevich Lebedev (1866-1912) in 1899. In his experiments, a glass vessel was used, from which air was pumped out. Inside the vessel, on a thin silver thread, were suspended yokes of torsion balances with thin disk-wings made of mica fixed to them (they were exposed to radiation). It was Lebedev who experimentally confirmed the validity of Maxwell's theory of light pressure.
The idea of a solar sail is simple in its essence - a spacecraft unfolds a large canvas - a sail that reflects or absorbs photons of light. Such a sail should have an area of hundreds of square meters or even several kilometers. In space, in the absence of gravity, such dimensions are not a problem.
The main disadvantage of a solar sail is that it can only move the ship away from the Sun, not towards it. The main and most important advantage of a solar sail is the complete absence of fuel costs.
At first glance, the space sail is very slow. Indeed, the initial stages of its acceleration will resemble turtle races. However, we must remember that the sail is constantly accelerating. For a sail weighing 0.8 g/m2, the initial acceleration will be 1.2 mm/s2. In the conditions of airless space, this will allow to achieve huge speeds in a very short time.
According to calculations, a ship with a space sail is capable of reaching speeds of 100,000 km / s and even higher. If such a probe had been launched into space in 2010, then, according to calculations, in 2018 it would have caught up with Voyager 1, launched in 1977 and already beyond the solar system.
The simplest and most reliable (but heavier, and therefore not too fast) solar sail has a frame structure. Most of all, it resembles a kite - a light cruciform frame is the supporting basis for four triangular sails, securely fastened to it. The shape of the frame can be different, even round.
Currently, the solar sail is the most promising device for movement in space, which has a number of advantages over chemical rocket engines.
What physical phenomenon underlies the operation of a solar sail?
Sample VPR 2018 in physics Grade 11 with answers. All-Russian test work of 2018 in physics grade 11, contains 18 tasks. To complete the work in physics, 1 hour 30 minutes (90 minutes) is allotted.
1. Read the list of concepts that you met in the course of physics:
electrical capacity, pascal, liter, energy, henry, density
Divide these concepts into two groups according to your chosen attribute. Write in the table the name of each group and the concepts included in this group.
| Concept group name | Concepts |
2. Choose two true statements about physical quantities or concepts. Write down their numbers in response.
1. Elastic deformations are called, which disappear after the action of external forces ceases.
2. With uniformly accelerated motion, the body travels the same distance every hour.
3. The kinetic energy of a body depends on the height at which the body is above the Earth's surface.
4. The Ampère force is the force with which the electric field acts on charged particles.
5. Photons have no rest mass and move in vacuum at a speed equal to the speed of light in vacuum.
3. When air flows out of an inflated balloon, it starts to move (see figure).
What is this type of motion called in physics?
4. Read the text and fill in the gaps with phrases from the list below.
The figure shows the moment of the demonstration experiment to test Lenz's rule, when all objects are stationary. The south pole of the magnet is inside the solid metal ring, but does not touch it. Rocker with metal rings can freely rotate around the vertical support. If you start to push the magnet out of the solid ring, then the ring will be _______________________________. If the magnet start ______________________ with a cut, then the ring will be ___________________________.
List of phrases
stay still
follow the magnet
repel a magnet
oscillate
pull out of the ring
push into the ring
5. A slightly inflated and tied ball was placed under the bell of the air pump. As air is pumped out from under the bell, the balloon inflates (see figure). How does the volume of air in the balloon, its pressure and density change?
For each value, determine the nature of the change and put the sign "٧" in the table in the desired cell of the table.
6. The connected system of elementary particles contains 9 electrons, 10 neutrons and 8 protons. Using a fragment of the Periodic system of elements D.I. Mendeleev, determine whether this bound system is an ion or a neutral atom of which element.
7. Figures A, B, C show the emission spectra of atomic vapors of strontium, an unknown sample, and calcium. Does the sample contain strontium and calcium? Explain the answer.
8. Water, the initial temperature of which is 25 ° C, is heated on a stove of constant power. It took an energy of 100 kJ to heat water to the boiling point. Further, 40 kJ was spent on boiling water. Depict the described processes on a graph of the dependence of water temperature on the energy received.
9. In the summer, Andrey lives in a country house, in which the electrical wiring is made with copper wires with a cross section of 1.5 mm2. The line for sockets is equipped with a circuit breaker with a trip setting of 16A (the circuit opens when this current value is exceeded). The voltage of the electrical network is 220 V.
The table shows the electrical appliances used in the house and the power they consume.
The house has an electric heater. Which of the following devices can be connected to the network in addition to the heater? Write down the solution and the answer.
10. The atmospheric pressure was measured using a barometer. The upper scale of the barometer is graduated in mm Hg. Art., and the lower scale is in hPa (see figure). The error in pressure measurements is equal to the division value of the barometer scale.
Write down the barometer reading in mm Hg. Art. taking into account the measurement error.
11. The astronauts investigated the dependence of gravity on the mass of the body on the planet they visited. The measurement error of gravity is 2.5 N, and body weight is 50 g. The measurement results, taking into account their error, are shown in the figure.
What is the approximate free fall acceleration on this planet?
12.
A magnet is inserted into the inductor. In this case, an induction current arises in its winding. You need to investigate whether the direction of the induction current that occurs in the coil depends on the direction of the vector
magnetic induction of the magnet. The following equipment is available (see picture):
- inductor;
- ammeter (on the scale of which "0" is in the middle);
- magnet;
- connecting wires.
In response:
1. Describe the experimental setup.
2. Describe the procedure for conducting research.
13.
Establish a correspondence between technical devices and physical phenomena underlying the principle of their operation.
For each position in the first column, select the corresponding position from the second column.
Technical devices
A. DC motor
B. incandescent lamp
physical phenomena
1) interaction of permanent magnets
2) the effect of a magnetic field on a conductor with current
3) thermal effect of current
4) chemical effect of current
Read the fragment of the instructions for the washing machine and complete tasks 14 and 15.
Before plugging in the machine, connect the ground wire to the water pipe if it is made of metal. If water is supplied through pipes made of synthetic material such as vinyl, grounding cannot be made to the water pipe. You must use another method of grounding.
Caution: Do not connect the ground wire to a gas pipe, lightning rod, telephone lines, etc.
For maximum safety, connect the ground wire to a copper plate or ground stake and bury the plate or stake in the ground to a depth of at least 20 cm.
14. The instructions require you to connect the ground wire when installing the washing machine. What is grounding for?
15. Why is it forbidden in the instructions to make a ground through a water pipe made of a synthetic material such as vinyl?
Read the text and do tasks 16-18.
X-rays
X-rays are electromagnetic waves whose photon energy lies on the electromagnetic wave scale between ultraviolet radiation and gamma radiation.
X-rays are always generated when electrons moving at high speed are retarded by the anode material (for example, in a low-pressure gas discharge tube). Part of the energy that is not dissipated in the form of heat is converted into electromagnetic wave energy (X-rays).
There are two types of X-rays: bremsstrahlung and characteristic. Bremsstrahlung X-ray radiation is not monochromatic, it is characterized by a variety of wavelengths, which can be represented as continuous
(continuous) spectrum.
The characteristic X-ray radiation has not a continuous, but a line spectrum. This type of radiation occurs when a fast electron, reaching the anode, knocks out electrons from the inner electron shells of the anode atoms. Empty spaces in the shells are occupied by other electrons of the atom. In this case, X-ray radiation is emitted with an energy spectrum characteristic of the anode material.
Monochromatic X-rays, whose wavelengths are comparable to the size of atoms, are widely used to study the structure of substances. This method is based on the phenomenon of X-ray diffraction on a three-dimensional crystal lattice. X-ray diffraction on single crystals was discovered in 1912 by M. Laue. Directing a narrow beam of X-rays at a stationary crystal, he observed a diffraction pattern on a plate placed behind the crystal, which consisted of a large number of spots arranged in a certain order.
The diffraction pattern obtained from a polycrystalline material (such as metals) is a set of clearly defined rings. From amorphous materials (or liquids) a diffraction pattern with fuzzy rings is obtained.
16. What type of X-ray radiation has a line spectrum?
17. The figures show diffraction patterns obtained on a single crystal, metal foil, and water. Which of the patterns corresponds to diffraction on a single crystal?
18. Is it possible to study the atomic structure of a single crystal using infrared rays? Explain the answer.
Answers to the VPR Sample 2018 in Physics Grade 11
1.
Concept group name
Physical quantities
Units of physical quantities
Concepts
Density, energy, electrical capacity
Henry pascal liter
2. 15
3. jet propulsion (or jet)
4. follow the magnet slide into the ring / pull out of the ring remain stationary
5.
The volume of air in the balloon increases.
The air pressure in the balloon decreases.
The air density in the balloon decreases.
6. oxygen ion
7. The spectrum of the sample contains the spectral lines of atomic strontium, but there are no spectral lines of calcium. Therefore, the unknown sample contains strontium but no calcium.
8.
9. The maximum power for which the wiring is designed, P = IU\u003d 16 220 \u003d 3520 watts.
The total power of all electrical appliances included in the network should not exceed 3.5 kW. The electric heater has a power of 2000 watts. This means that at the same time it can be connected to the network either only an iron, or only a TV, or only a microwave oven. Or you can simultaneously turn on the TV and microwave oven (their total power consumption is 1300 W)
10. (744 ± 1) mmHg Art.
11. any value in the range from 7.3 to 8.8 m/s 2
12.
1) The setting shown in the figure is used. The coil is connected to an ammeter. The magnet is introduced into the coil and the appearance of an induction current is observed.
2) The direction of the magnetic induction vector of the magnet is changed by introducing the magnet into the coil first with the north and then with the south pole. In this case, the speed of movement of the magnet in two experiments is approximately the same.
3) The direction of the induction current is judged by the direction of deviation of the ammeter needle.
13. 23
14. In the event of a power failure on the machine, the body of the machine may become live.
If the body of the machine is grounded, then when you touch it, no current will flow through the human body, since its resistance is much greater than the resistance of the ground wire.
15. A pipe made of plastic (vinyl) does not conduct electricity, and therefore cannot be used for grounding.
16. characteristic x-rays
17. 2
18.
1) You can't.
2) The wavelengths of infrared radiation are much larger than the size of atoms, so the infrared rays will go around the atoms (“without noticing” them)
1. The figures show graphs of the dependence of the power of an incandescent lamp P \u003d P (T) and the resistance of its spiral R \u003d R (T) on temperature. Choose two true statements that can be made by analyzing these graphs.
1) The resistance of the lamp spiral with an input power P \u003d 200 W is 124 ohms.
2) With increasing temperature, the voltage on the lamp filament decreases.
3) With a lamp coil resistance of 80 ohms, the voltage across the lamp coil is 70 V.
4) With a lamp coil resistance of 100 ohms, the voltage across the lamp coil is 100 V.
5) The voltage on the lamp filament with input power P = 150 W is more than 140 V.
2. The figure shows a graph of the dependence of the current strength on time in an oscillatory circuit formed by a capacitor and a coil, the inductance of which is 0.3 H.
1) The period of electromagnetic oscillations is 4 ms.
2) The maximum value of the energy of the electric field of the capacitor is 5.4 μJ.
3) At the time of 4 ms, the charge of the capacitor is zero.
4) At a time of 3 ms, the energy of the magnetic field of the coil reaches its minimum.
3.
1) The period of electromagnetic oscillations is 5 ms.
2) The maximum value of the energy of the electric field of the capacitor is 0.9 μJ.
3) At the moment of time 3 ms the charge of the capacitor is equal to zero.
4) At the time of 4 ms, the energy of the magnetic field of the coil reaches its minimum.
5) During the first 6 ms, the energy of the magnetic field of the coil reached its maximum 2 times.
4.
3) The EMF module of the self-induction of the coil at the time t = 2.0 s is 2.4 V.
4) The voltage across the resistor at time t = 1.0 s is 1.9 V.
5) The EMF of the current source is 18 V.
5. The inductor is connected to a current source with a negligible internal resistance through a resistor R = 60 Ohm (see figure). At the moment t = 0, the key K is closed. The values of the current strength in the circuit, measured at successive points in time with an accuracy of 0.01 A, are presented in the table. The coil wire resistance is negligible.
1) The energy of the coil is maximum at the time t = 0 s.
3) The voltage across the resistor at time t = 2.0 s is 2.6 V.
4) The EMF module of the self-induction of the coil at the time t \u003d 1.5 s is 4.2 V.
5) The EMF of the current source is 15 V.
6. A metal body, the longitudinal section of which is shown in the figure, was placed in a uniform electric field of strength E.
2) The potentials at points A and C are equal.
3) The concentration of free electrons at point B is the highest.
4) A positive charge is induced at point A.
5) A negative charge is induced at point D.
7. A metal body, the longitudinal section of which is shown in the figure, was placed in a uniform electric field of strength E.
From the list below, select two correct statements describing the results of the action of this field on a metal body, and indicate their numbers.
2) The potential at point A is less than at point D.
3) The concentration of free electrons at point A is the smallest.
4) A positive charge is induced at point C.
5) A negative charge is induced at point B.
8.
2) The refractive index of glass is approximately 1.22.
3) The angle of refraction is 50°.
4) The speed of light is faster in air than in glass.
5) Reflection angle is 70°.
9. The schoolboy, studying the laws of geometric optics, conducted an experiment on the refraction of light (see figure). To do this, he directed a narrow beam of light onto a glass plate. Using the table below, select two correct statements from the list below and indicate their numbers.
2) The refractive index of glass is approximately 1.47.
3) The angle of refraction is 40°.
4) The speed of light is slower in air than in glass.
5) Reflection angle is 20°.
10.
1) When the voltage on the lamp is 80 V, the thermal power released on the lamp is 80 W.
2) At a heat loss power of 150 W, the temperature of the lamp filament is less than 3000 K.
3) With a current through the lamp of 2 A, the temperature of the filament is about 3600 K.
4) With an increase in the current through the lamp, the temperature of its spiral increases.
5) With a heat loss power of 100 W, the lamp voltage is 100 V.
11. When the filament of an incandescent lamp is heated by an electric current flowing through it, the main part of the input energy is lost in the form of thermal radiation. The figure shows graphs of the dependence of the heat loss power of the lamp on the temperature of the spiral P = P(T) and the current strength on the applied voltage I = I(U).
Choose two correct statements about the physical quantities that characterize this process.
1) With increasing voltage on the lamp, the temperature of its spiral increases.
2) At a heat loss power of 50 W, the temperature of the lamp filament is more than 2800 K.
3) With a current through the lamp of 1.5 A, the temperature of the filament is less than 3000 K.
4) When the voltage on the lamp is 100 V, the thermal power released on the lamp is 80 watts.
5) With a heat loss power of 150 W, the lamp voltage is 100 V.
12. In the first experiment, a current flows through the wire resistor. In the second experiment, it was replaced with another resistor made of wire of the same cross section of the same metal, but twice as long. Half the current was passed through the second resistor.
Choose two correct statements about the physical quantities that characterize this process.
1) The thermal power released on the resistor remained the same.
2) The resistance of the resistor has increased by 2 times.
3) The resistance of the resistor has decreased by 2 times.
5) The thermal power released on the resistor has decreased by 2 times.
13.
1) During the first second, no current flows through the resistor.
2) At time t = 2 s, the voltage across the capacitor is 5.2 V.
3) During the entire observation time, the capacitor is charged.
4) The EMF of the current source is 12 V.
5) At time t = 4 s, the voltage across the capacitor is 4.9 V.
14. The capacitor is connected to a current source in series with a resistor R = 20 kOhm (see figure). At time t = 0, the switch is closed. At this point, the capacitor is completely discharged. The results of measurements of the current strength in the circuit, performed with an accuracy of ±1 μA, are presented in the table.
Choose two statements corresponding to the results of this experiment, and indicate their numbers. Ignore the internal resistance of the source and the resistance of the wires.
1) The EMF of the current source is 6 V.
2) By the time t = 2 s, the capacitor is fully charged.
3) At time t = 3 s, the voltage across the capacitor is 0.3 V.
5) At time t = 4 s, the voltage across the capacitor is 5.9 V.
15. In an ideal oscillatory circuit, consisting of a capacitor and an inductor, free electromagnetic oscillations occur. The table shows the values of the potential difference on the capacitor plates at successive times.
1) The period of oscillation isWith.
2) The oscillation frequency is 125 kHz.
3) At the moment
4) At the momentwith the maximum current in the circuit.
5) At the momentwith the energy of the coil is zero.
In an ideal oscillatory circuit, consisting of a capacitor and an inductor, free electromagnetic oscillations occur. The table shows the values of the current in the coil of this circuit at successive times.
1) The period of oscillation isWith.
2) The oscillation frequency is 25 kHz.
3) At the moment t =with the maximum voltage across the capacitor.
4) At the moment t =with minimum coil energy.
5) At the moment t =
17.
1) The EMF module of the self-induction of the coil at the time t \u003d 1.0 s is 7.6 V.
2) The EMF module of the self-induction of the coil at the time t = 2.0 s is 1.6 V.
3) The EMF of the current source is 4.8 V.
4) The voltage across the resistor increases monotonically over time.
18. The inductor is connected to a current source with a negligible internal resistance through a resistor R = 40 Ohm (see figure). At the moment t = 0, the key K is closed. The values of the current strength in the circuit, measured at successive points in time with an accuracy of ±0.01 A, are presented in the table.
1) The EMF module of the self-induction of the coil at the time t = 1.0 s is 4.4 V.
2) The EMF module of the self-induction of the coil at the time t = 2.0 s is 7.6 V.
3) The EMF of the current source is 12 V.
4) The voltage across the resistor decreases monotonically over time.
5) By the time t = 3 s, the EMF of the self-induction of the coil is zero.
19. Two small fixed beads located at points A and B carry charges +q > 0 and -2q, respectively (see figure). Point C is in the middle between beads A and B.
From the list below, select two correct statements and indicate their numbers.
1) The Coulomb force acts on the bead B from the side of the bead A, directed horizontally to the right.
2) The strength of the resulting electrostatic field at point C is directed horizontally to the left.
3) The modules of the Coulomb forces acting on the beads are the same.
4) If the beads are connected with a thin copper wire, they will repel each other.
20. Two small fixed beads located at points A and B carry charges +q > 0 and -2q, respectively (see figure). Point C is in the middle between points A and B. From the list below, select two correct statements and indicate their numbers.
1) On bead A, from the side of bead B, the Coulomb force acts, directed horizontally to the right.
2) The strength of the resulting electrostatic field at point C is directed horizontally to the right.
3) The modulus of the Coulomb force acting on bead B is 2 times greater than the modulus of the Coulomb force acting on bead A.
4) If the beads are connected with a thin copper wire, they will attract each other.
5) If the beads are connected with an uncharged glass rod, their charges will become equal.
21.
From the list below, select two correct statements and indicate their numbers.
1) The charge of the plate is negative.
2) The potential at point B is less than at point C.
3) The work of the forces of the electrostatic field to move a point negative charge from point A to point B is zero.
4) If a point negative charge is placed at point A, then a force directed vertically downwards will act on it from the side of the plate.
22. The capacitor is connected to a current source in series with a resistor R = 20 kOhm (see figure). At time t = 0, the switch is closed. At this point, the capacitor is completely discharged. The results of measurements of the current strength in the circuit, performed with an accuracy of ±1 μA, are presented in the table.
1) The current in the circuit decreases in direct proportion to time.
2) The EMF of the current source is 6.0 V.
4) At time t = 3 s, the voltage across the capacitor is 0.3 V.
5) At time t = 3 s, the voltage across the capacitor is 5.7 V.
23. The figure shows the lines of intensity of a uniform electrostatic field formed by a uniformly charged extended plate.
From the list below, select two correct statements and indicate their numbers.
1) The charge on the plate is positive.
2) The potential at point B is greater than at point C.
3) The work of the forces of the electrostatic field to move a point positive charge from point A to point B is positive.
4) If a point negative charge is placed at point B, then a force directed vertically upwards will act on it from the side of the plate.
24. The capacitor is connected to a current source in series with a resistor R = 40 kOhm (see figure). At time t = 0, the switch is closed. At this point, the capacitor is completely discharged. The results of measurements of the current strength in the circuit, performed with an accuracy of ±1 μA, are presented in the table.
1) The EMF of the current source is 12 V.
2) The current in the circuit decreases in direct proportion to time.
3) The voltage on the capacitor at any time is equal to the EMF of the source.
4) At time t = 2 s, the voltage across the capacitor is 10.4 V.
5) At time t = 2 s, the voltage across the capacitor is 1.6 V.
25.
Choose two true statements about the process taking place in the circuit:1) The period of oscillation isWith.
2) At the moment t =
3) At the moment t =with the maximum energy of the capacitor.
4) At the moment t =
5) The oscillation frequency is 25 kHz.
26. In an ideal oscillatory circuit, free electromagnetic oscillations occur. The change in the charge of one of the capacitor plates in the oscillatory circuit over time is shown in the table.
Choose two true statements about the process taking place in the circuit:1) The period of oscillation isWith.
2) At the moment t =with the maximum energy of the coil.
3) At the moment t =with the energy of the capacitor is minimal.
4) At the moment t =s current in the circuit is 0.
5) The oscillation frequency is 62.5 kHz.
27. The glass lens (refractive index of glass n1 = 1.54) shown in the figure was transferred from air (n2 = 1) to water (n3 = 1.33). Select two correct statements about the nature of the changes that have occurred with the lens.
1) The lens has changed from divergent to converging.
2) The focal length has decreased, the optical power has increased.
4) The focal length has increased, the optical power has decreased.
5) The lens remained converging.
1. Answer: 14. 2. Answer: 12. 3. Answer: 34. 4. Answer: 35. 5. Answer: 24.
28. The glass lens (refractive index of glass (n1 = 1.54), shown in the figure, was transferred from water (n2 = 1.33) to air (n3 = 1). Select two correct statements about the nature of the changes that occurred with the lens.
1) The lens remained converging.
2) The lens has changed from divergent to converging.
3) The lens has changed from converging to diverging.
4) The focal length has decreased, the optical power has increased.
5) The focal length has increased, the optical power has decreased.
Answers:
6. Answer: 23. 7. Answer: 45. 8. Answer: 45. 9. Answer: 23. 10.Answer: 34.
11. Answer: 13. 12. Answer: 25. 13. Answer: 23. 14. Answer: 15. 15. Answer: 23.
16. Answer: 13. 17. Answer: 24. 18. Answer: 13. 19. Answer: 34. 20. Answer: 12.
21. Answer: 34. 22. Answer: 25. 23. Answer: 12. 24. Answer: 14. 25. Answer: 13.
26. Answer: 25. 27. Answer: 45. 28. Answer: 14.
