Physics Test

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Physics Test - 2

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Question 1
4 / -1

A radio transmitter operates at a frequency 880 kHz and a power of 10 kW . The number of photons emitted per second is:

A

B

C

D

Solution
Question 2
4 / -1

If a body is rolling down from a hill at certain height, the body will have:

A
Kinetic Energy only

B
Rotational energy and Kinetic energy only

C
Potential energy only

D
Kinetic energy, Rotational energy and potential energy
Solution
If a body is rolling down a hill at some height, then the system will have kinetic energy, rotational energy and potential energy.
- Kinetic energy: Since the body is moving in a linear direction, so it will have kinetic energy due to its velocity.
- Rotational energy: Along with linear velocity, the body is also revolving i.e. rotating, so it will have rotation energy.
- Potential energy: Since the body is at a certain height, it will have potential energy.
- The body will have all three Kinetic energy, Rotational energy, and potential energy.
Question 3
4 / -1

A geyser heats water flowing at the rate of 3.0 litres per minute from 27^∘C to 77^∘ C. If the geyser operates on a gas burner, what is the rate of consumption of the fuel if its heat of combustion is 4.0 × 10⁴ J/g?

A

B

C

D

Solution
Question 4
4 / -1

According to Gauss’s law, if E is _________, the charge density in the ideal conductor is zero.

A
Positive

B
Negative

C
Zero

D
Unity

Solution

The Electric Field for a uniformly distributed spherical charge is given by

Gauss' law states that the electric flux through any closed surface is equal to the total charge inside divided by ε₀.

Charges are the source and sinks of the electric field. Since in a conducting material the electric field is everywhere zero, the divergence of E is zero, and by Gauss law, the charge density in the interior of the conductor must be zero.
Question 5
4 / -1

What is the direction of force of friction acting on a body moving on a fixed surface?

A
Along the different of motion

B
Opposite to the direction of motion

C
Independent of Motion

D
Both (A) and (B)

Solution

When we try to slide a body on a surface, the motion of the body is opposed by a force called the force of friction. The frictional force arises due to intermolecular interaction.

When an external force (F) is applied to move the body and the body does not move, then the frictional force acts opposite to applied force F and is equal to the applied force i.e., F − f = 0. When the body remains at rest, the frictional force is called the static friction. Static friction is a self-adjusting force.

Friction force, f_s = μmg

Where, μ_s = coefficient of friction.

Thus, friction force act opposite to the direction of motion.
Question 6
4 / -1

What amount of heat must be supplied to 2.0 × 10⁻²kg of Nitrogen (at room temperature) to raise its temperature by 45^∘C at constant pressure? (Molecular mass of N₂ = 28; R = 8.3Jmol⁻¹K⁻¹.

A

B

C

D

Solution
Question 7
4 / -1

Which of the following is Kilowatt-hour a unit of?

A
Power

B
Force

C
Energy

D
Momentum

Solution

Kilowatt-hour is the unit of energy. The capacity to do work or power consumed in a given time is called energy. Power is the rate of doing work or the rate at which energy is spent.
Question 8
4 / -1

When two vectors in the same direction are added, the magnitude of the resulting vector is equal to _______.

A
Sum of magnitudes of the vectors

B
Difference of magnitudes of the vectors

C
Product of magnitudes of the vectors

D
Sum of the roots of magnitudes of the vectors

Solution

When two vectors in the same direction are added, the magnitude of the resulting vector is equal to the sum of magnitudes of the vectors.

Consider the graphical representation of these two vectors. When one vector is added to the other in the same direction, the lengths will be added. The resultant vector will bear the resultant length. Length is the magnitude of the vector. Hence the magnitudes add to give the magnitude of the resultant vector.
Question 9
4 / -1

Select the correct statement regarding plane mirror:

A
The laws of reflection of light is only true for the plane mirror

B
The plane mirror always forms real images

C
The plane mirror may form a virtual image

D
The virtual image is always erect
Solution
Plane Mirror: A plane mirror is a mirror with a flat (planar) reflective surface.

The characteristics of an image formed in a plane mirror:
- The image formed by the plane mirror is virtual and erect i.e., image cannot be projected or focused on a screen.
- The distance of the image ‘behind’ the mirror is the same as the distance of the object in front of the mirror.
- The size of the image formed is the same as the size of the object.
- The image is laterally inverted, i.e., left hand appears to be the right hand when seen from the plane mirror.
- If the object moves towards (or away from) the mirror at a certain rate, the image also moves towards (or away from) the mirror at the same rate.
- The laws of reflection are true for both plane mirrors as well as spherical mirrors.
- The plane mirror always forms the virtual and erect images.
Question 10
4 / -1

A long insulated copper wire is closely wound as a spiral of 'N' turns. The spiral has an inner radius 'a' and an outer radius 'b'. The spiral lies in the X-Y plane and a steady current 'I' flows through the wire. The Z-component of the magnetic field at the center of the spiral is:

A

B

C

D

Solution

Let us consider an elementary ring of radius r and thickness dr in which current I is flowing.