CBSE PHYSIC PRACTICE TEST-2023

Section A: Multiple Choice Questions

Which of the following is not a fundamental unit?

a. metre

b. kilogram

c. second

d. joule

Which of the following is a vector quantity?

a. mass

b. speed

c. distance

d. displacement

A body is moving with a uniform speed of 10 m/s. Which of the following is true?

a. Its acceleration is zero.

b. Its velocity is zero.

c. Its displacement is zero.

d. Its momentum is zero.

The force required to maintain the motion of a body in a circular path is called:

a. frictional force

b. centripetal force

c. gravitational force

d. normal force

The mass of a proton is approximately:

a. 1.6 x 10^-27 kg

b. 1.6 x 10^-24 kg

c. 1.6 x 10^-19 kg

d. 1.6 x 10^-16 kg

Which of the following is a non-contact force?

a. Frictional force

b. Tension force

c. Magnetic force

d. Normal force

The SI unit of power is:

a. Watt

b. Joule

c. Newton

d. Meter

The velocity-time graph of a particle is a straight line parallel to the time axis. What does this indicate?

a. The particle is at rest.

b. The particle is moving with constant velocity.

c. The particle is accelerating.

d. The particle is moving with increasing velocity.

Which of the following is an example of periodic motion?

a. A ball thrown up in the air

b. A stone dropped from a height

c. A simple pendulum

d. A car moving on a straight road

An object is dropped from a height of 20 m. What is its velocity just before it hits the ground?

a. 20 m/s

b. 40 m/s

c. 0 m/s

d. Cannot be determined.

Section B: Short Answer Questions

What is the difference between scalar and vector quantities?

Define the term 'work' and write its SI unit.

What is Newton's Second Law of Motion?

What is the principle of conservation of energy?

Explain the term 'momentum' and write its formula.

What is the difference between elastic and inelastic collisions?

Define the term 'potential difference' and write its SI unit.

What is the formula for force of friction between two surfaces in contact?

What is the principle of superposition of waves?

Explain the term 'angular velocity' and write its formula.

Section C: Long Answer Questions

A car is moving with a speed of 20 m/s. It comes to a stop in 10 seconds. Calculate the average acceleration of the car.

State the Law of Conservation of Linear Momentum. Explain its applications in daily life.

Derive the formula for potential energy of a body at a height h above the ground.

A body is moving in a circular path with a uniform speed of 5 m/s. If the radius of the circle is 10 m, calculate the centripetal force acting on the body.

Define the term 'wave' and explain the difference between transverse and longitudinal waves.

Explain the concept of work done by a force. Derive the formula for work

ANSWERS: YOU CAN REFER THE ANSWERS FOR THE ABOVE QUESTIONS BELOW"

Here are the answers to the physics test paper for Grade 11, CBSE scheme Indian syllabus:

Section A: Multiple Choice Questions

Which of the following is not a fundamental unit?

Answer: d. joule

Which of the following is a vector quantity?

Answer: d. displacement

A body is moving with a uniform speed of 10 m/s. Which of the following is true?

Answer: a. Its acceleration is zero.

The force required to maintain the motion of a body in a circular path is called:

Answer: b. centripetal force

The mass of a proton is approximately:

Answer: a. 1.6 x 10^-27 kg

Which of the following is a non-contact force?

Answer: c. Magnetic force

The SI unit of power is:

Answer: a. Watt

The velocity-time graph of a particle is a straight line parallel to the time axis. What does this indicate?

Answer: b. The particle is moving with constant velocity.

Which of the following is an example of periodic motion?

Answer: c. A simple pendulum

An object is dropped from a height of 20 m. What is its velocity just before it hits the ground?

Answer: c. 0 m/s

Section B: Short Answer Questions

What is the difference between scalar and vector quantities?

Answer: Scalar quantities are those that have only magnitude, while vector quantities have both magnitude and direction.

Define the term 'work' and write its SI unit.

Answer: Work is the product of the force and the displacement of an object in the direction of the force. Its SI unit is Joule (J).

What is Newton's Second Law of Motion?

Answer: Newton's Second Law of Motion states that the acceleration of an object is directly proportional to the force acting on it and inversely proportional to its mass.

What is the principle of conservation of energy?

Answer: The principle of conservation of energy states that energy can neither be created nor destroyed but can only be transformed from one form to another.

Explain the term 'momentum' and write its formula.

Answer: Momentum is the product of the mass and velocity of an object. Its formula is p = mv.

What is the difference between elastic and inelastic collisions?

Answer: In elastic collisions, the total kinetic energy of the colliding bodies is conserved, while in inelastic collisions, some of the kinetic energy is lost in the form of heat, sound, or deformation.

Define the term 'potential difference' and write its SI unit.

Answer: Potential difference is the amount of work required to move a unit charge from one point to another in an electric field. Its SI unit is volt (V).

What is the formula for force of friction between two surfaces in contact?

Answer: The formula for force of friction between two surfaces in contact is Ff = μN, where Ff is the force of friction, μ is the coefficient of friction, and N is the normal force.

What is the principle of superposition of waves?

Answer: The principle of superposition of waves states that when two or more waves meet at a point, the displacement of the resultant wave at that point is the sum of the displacements of the individual waves.

Explain the term 'angular velocity' and write its formula.

Answer: Angular velocity is the rate of change of angular displacement of an object. Its formula is ω = Δθ/Δt.

Section C: Long Answer Questions

A car is moving with a speed of 20 m/s. It comes to a stop

after applying the brakes, covering a distance of 40 m. Calculate the acceleration of the car during this process.

Answer: Initial velocity, u = 20 m/s

Final velocity, v = 0 m/s

Distance covered, s = 40 m

Using the equation v^2 - u^2 = 2as, we get:

0 - (20)^2 = 2a(40)

-400 = 80a

a = -5 m/s^2

Therefore, the acceleration of the car during this process is -5 m/s^2.

State and explain Kepler's laws of planetary motion.

Answer:

Kepler's laws of planetary motion are:

i. Law of orbits: Every planet in the solar system moves around the sun in an elliptical orbit, with the sun at one of the foci of the ellipse.

ii. Law of areas: The line joining a planet to the sun sweeps out equal areas in equal intervals of time. This means that a planet moves faster when it is closer to the sun and slower when it is farther away.

iii. Law of periods: The square of the time period of revolution of a planet around the sun is proportional to the cube of its average distance from the sun.

Explanation: Kepler's laws of planetary motion provide a mathematical description of the motion of planets around the sun. According to these laws, the orbits of planets are elliptical, with the sun at one of the foci of the ellipse. The speed of the planet changes as it moves around its orbit, and the time taken for one complete revolution around the sun depends on its distance from the sun. These laws helped in the development of the laws of gravitation by Isaac Newton.

Derive the formula for the magnifying power of a simple microscope.

Answer:

Magnifying power of a simple microscope is given by the formula:

M = 1 + (f/fe)

where M is the magnifying power, f is the focal length of the lens, and fe is the least distance of distinct vision.

Derivation:

Let the object be placed at a distance u from the lens and the image be formed at a distance v from the lens. Using the thin lens formula, we get:

1/u + 1/v = 1/f

Rearranging the terms, we get:

v = uf/(u + f)

The magnification produced by the lens is given by the ratio of the height of the image to the height of the object. For a small object, the height of the object is approximately equal to the distance between the object and the lens. Hence,

Magnification, m = v/u = f/(u + f)

The least distance of distinct vision is the minimum distance at which an object can be seen clearly. For a normal eye, it is about 25 cm or 0.25 m. Hence, fe = 0.25 m.

Substituting the values of v and fe in the magnification formula, we get:

M = v/fe = (uf/(u + f))/fe

Simplifying this expression, we get:

M = 1 + (f/fe)

Explain the process of charging a capacitor.

Answer:

A capacitor is a device that stores electric charge. It consists of two conducting plates separated by a dielectric material. To charge a capacitor, we need to connect it to a voltage source.

When a voltage source is connected to the capacitor, the potential difference between the plates increases, causing electrons to flow from the negative terminal of the source to the negative plate of the capacitor. As a result, the negative plate becomes negatively charged and the positive plate becomes positively charged.

As the charge builds up on the plates, the potential difference across the

capacitor increases until it reaches the same value as the voltage of the source. At this point, the capacitor is fully charged and no more current flows.

The time taken to charge a capacitor depends on the capacitance of the capacitor and the resistance of the circuit. The charging process follows an exponential curve, and the capacitor reaches 63.2% of its full charge after one time constant, where time constant is equal to the product of the capacitance and resistance of the circuit.

To discharge a capacitor, we need to remove the voltage source and connect a resistor across the capacitor. The charge on the plates starts to flow through the resistor, causing the voltage across the capacitor to decrease exponentially. The time taken for the voltage to decrease to 37% of its initial value is one time constant.

Explain the process of nuclear fission and its importance in the generation of nuclear power.

Answer:

Nuclear fission is a process in which the nucleus of an atom is split into two smaller nuclei with the release of a large amount of energy. This process can occur spontaneously, but it can also be induced by bombarding the nucleus with neutrons.

In a nuclear reactor, a controlled chain reaction is initiated by bombarding the fuel (usually uranium-235) with neutrons. When a neutron collides with a uranium-235 nucleus, it causes the nucleus to split into two smaller nuclei (fission products), releasing two or three neutrons and a large amount of energy. These neutrons can then go on to collide with other uranium-235 nuclei, causing a chain reaction.

The energy released during nuclear fission is used to heat water and produce steam, which drives turbines to generate electricity. The use of nuclear power has several advantages, including the ability to generate large amounts of electricity with relatively small amounts of fuel, and the absence of greenhouse gas emissions.

However, there are also several disadvantages, including the potential for accidents and the production of radioactive waste that needs to be stored safely for thousands of years.

State the principle of the working of a transformer and derive the expression for the voltage ratio of a transformer.

Answer:

The principle of the working of a transformer is based on the phenomenon of electromagnetic induction. A transformer consists of two coils, the primary coil and the secondary coil, wound around a common magnetic core. When an alternating current flows through the primary coil, it creates a changing magnetic field around the coil, which induces an alternating electromotive force (EMF) in the secondary coil.

The voltage ratio of a transformer is given by the formula:

Vp/Vs = Np/Ns

where Vp is the voltage across the primary coil, Vs is the voltage across the secondary coil, Np is the number of turns in the primary coil, and Ns is the number of turns in the secondary coil.

Derivation:

Let the voltage across the primary coil be Vp and the voltage across the secondary coil be Vs. Let the number of turns in the primary coil be Np and the number of turns in the secondary coil be Ns.

The EMF induced in the secondary coil is given by Faraday's law of electromagnetic induction:

EMF = -dΦ/dt

where Φ is the magnetic flux through the coil.

The magnetic flux Φ is proportional to the number of turns of the coil and the magnetic field strength. Hence,

Φ = BAN

where B is the magnetic field strength, A is the area of the coil, and N is the number of turns.

Substituting this expression in Faraday's law, we get:

EMF = -d(BAN)/dt

EMF = -NAB/dt (since B is constant)

The voltage across the primary coil is given by Ohm's law:

Vp = I1R1

where I1 is the current flowing through the primary coil and R1 is the resistance of the primary coil.

Similarly, the voltage across the secondary coil is given by Ohm's law:

Vs = I2R2

where I2 is the current flowing through the secondary coil and R2 is the resistance of the secondary coil.

The power input to the transformer is equal to the power output, neglecting losses:

P = VpI1 = VsI2

Substituting the expressions for Vp and Vs in terms of I1 and I2, we get:

I1R1I1 = I2R2I2

I1^2R1 = I2^2R2

I1/I2 = √(R2/R1)

But I1/I2 = Ns/Np, since the current is conserved in a transformer.

Therefore, the voltage ratio of a transformer is given by:

Vp/Vs = Np/Ns = √(R1/R2)

This formula shows that the voltage ratio of a transformer depends on the ratio of the resistances of the coils, which is determined by the number of turns in each coil and the cross-sectional area of the wire.