Physics Test 53

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Physics Test 53

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Weekly Quiz Competition

Question 1
4 / -1

A rectangular loop of sides 8 cm and 2 cm with a small break in it is moving out of a region of uniform magnetic field of 0.3 T, directed normal to the loop. What is the emf developed across the break if the velocity of the loop is 1 cms^-1 in a direction normal to the longer side of the loop?

A
0.06 V

B
0.12 V

C
0.18 V

D
0.02 V

Solution

Given:

Length of the rectangular wire, l = 8 cm = 0.08 m

Width of the rectangular wire, b = 2 cm = 0.02 m

Hence, area of the rectangular loop,

A = lb

= 0.08 × 0.02

= 16 × 10−4 m²

Magnetic field strength, B = 0.3 T

Velocity of the loop, v = 1 cms^-1 = 0.01 ms^-1

Emf developed in the loop is given as:

e = Blv

= 0.3 × 0.08 × 0.01 = 2.4 × 10⁻⁴V

= 0.02 V

Hence, the correct option is (D).
Question 2
4 / -1

A liquid flows through pipes of different diameters. Velocity of liquid is 2 ms⁻¹. At the point where the diameter of the pipe is 6 cm.The velocity of liquid at a point where the diameter of the pipe is 3 cm will be

A
1 ms⁻¹

B
4 ms⁻¹

C
8 ms⁻¹

D
16 ms⁻¹

Solution
Question 3
4 / -1

Through which of the following modes of communication can radio waves be sent from one place to another?

A
Ground wave propagation.

B
Skywave propagation.

C
Space wave propagation.

D
All of the above.

Solution

Radio waves are generated artificially by transmitters and received by radio receivers, using antennas. Radio waves are very widely used in modern technology for fixed and mobile radio communication, broadcasting, radar and radio navigation systems, communications satellites, wireless computer networks and many other applications. Different frequencies of radio waves have different propagation characteristics in the Earth's atmosphere; long waves can diffract around obstacles like mountains and follow the contour of the earth (ground waves), shorter waves can reflect off the ionosphere and return to earth beyond the horizon (skywaves), while much shorter wavelengths bend or diffract very little and travel on a line of sight, so their propagation distances are limited to the visual horizon.

Hence, the correct option is (D).
Question 4
4 / -1

A block of mass m₂lying on a horizontal frictionless surface is connected to a block of mass m₁by means of a string that passes over a frictionless pulley as shown in the figure below. If m₁ > m₂, the common acceleration of the masses is given by (g is the acceleration due to gravity)

A
m₁ / m₂g

B
m₂ / m₁g

C
m₁ / (m₁ + m₂)g

D
m₂ / (m₁ + m₂)g

Solution
Question 5
4 / -1

Which of the following pairs has the same dimensions?

A
Specific Heat and Latent Heat

B
Impulse and Momentum

C
Surface Tension and Force

D
Moment of Inertia and Torque

Solution

Impulse has the same units and dimensions (MLT⁻¹) as momentum. In the International System of Units, these are kg × m/s = N × s, in English engineering units.

Hence, the correct option is (B).
Question 6
4 / -1

The half-life of 131I is 8 days. Given a sample of 131I at time t = 0, we can assert that

A
No nucleus will decay before t = 4 days

B
No nucleus will decay before t = 8 days

C
No nucleus will decay before t = 16 days

D
No nucleus will decay before t = 0 days

Solution

The number of nuclei decreases exponentially

N = N₀e^−λt

Therefore, decay process lasts upto t = α. Therefore, a given nucleus may decay at any time after t = 0.

Hence, the correct option is (D).
Question 7
4 / -1

A moving particle of mass m, makes a head-on elastic collision with another particle of mass 2 m, which is initially at rest. The percentage loss in energy of the colliding particle on collision is close to

A
50%

B
66.7%

C
90%

D
100%

Solution
Question 8
4 / -1

A small telescope has an objective lens of focal length 150 cm and an eyepiece of focal length 5 cm. if this telescope is used to view 100 m high towers 3 km away. Find the height of the final image when it is formed 25 cm away from the eyepiece.

A
-30 cm

B
-24 cm

C
28 cm

D
32 cm

Solution

The Magnifying power of a telescope is defined as the ratio of the angle subtended at the eye by the image formed at least distance of distinct vision to angle subtended at the eye by the object lying in infinity.
Question 9
4 / -1

A sphere of mass m and diameter D is Heated by temperature ΔT, if the Coefficient of linear expansion is a what will be the change in the Surface area?

A

B

C

D

Solution
Question 10
4 / -1

A bar magnet is dropped between a current carrying coil. What would be its acceleration?

A
g downwards

B
Greater than g downwards

C
Less than g downwards

D
Bar will be stationary

Solution

So, due to change in the flux emf is induced in the coil and by Lenz's law current flow in the direction which opposes the change in a magnetic field. So, the force due to this current-induced magnetic field opposes the motion of the bar magnet. Therefore, the net acceleration of fall is less than g.

Hence, the correct option is (C).