Physics Test

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Physics Test - 3

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Question 1
1 / -0

In an LCR series circuit, the potential difference between the terminals of the inductance is 60 V, that between the terminals of the capacitor is 30 V and that across the resistance is 40 V. Then, the supply voltage will be

A
50 V

B
70 V

C
130 V

D
10 V

Solution
Question 2
1 / -0

In an oscillating LC circuit, the maximum charge on the capacitor is Q. The charge on the capacitor, when energy is stored equally between the electric and magnetic fields, is

A
Q/2

B
Q/√2

C
Q/√3

D
Q/3

Solution

If energy is stored equally in electric and magnetic fields, then energy in electric field will be half of the maximum value, which occurs when the charge on the capacitor is maximum.
Question 3
1 / -0

A coil takes a current of 2 A and 200 W power from an alternating current source of 220 V, 50 Hz. What is the inductance of the coil?

A
0.312 H

B
0.142 H

C
0.285 H

D
1.07 H

Solution
Question 4
1 / -0

A circular metal plate of radius 'R' is rotating with a uniform angular velocity 'ω' with its plane perpendicular to a uniform magnetic field B. Then, emf developed between the centre and the rim of the plate is

A
πωBR²

B
ωBR²

C
πωBR²/2

D
ωBR²/2

Solution
Question 5
1 / -0

A needle made of bismuth is suspended freely in a magnetic field. The angle which the needle makes with the magnetic field is

A
0°

B
45°

C
90°

D
180°

Solution

Bismuth is a diamagnetic substance, so when placed in an external magnetic field it rotates such that its axis becomes perpendicular to the magnetic field.
Question 6
1 / -0

The magnetic susceptibility of a material of a rod is 449. Permeability of vacuum is 4π x 10^-7henry/metre. The absolute permeability of the material of the rod (in henry/metre) is

A
π x 10^-4

B
2π x 10^-4

C
3π x 10^-4

D
4π x 10^-4

Solution
Question 7
1 / -0

A magnet of length 10 cm and magnetic moment 1 Am² is placed along the side AB of an equilateral triangle ABC. If the length of side AB is 10 cm, then the magnetic field at point C is

A
10^-9 T

B
10^-7 T

C
10^-5 T

D
10^-4 T

Solution

Let m be the pole strength of each pole of the magnet figure. The magnetic field at C due to the N-pole is given by
Question 8
1 / -0

A magnetic dipole is acted upon by two magnetic fields which are inclined to each other at an angle of 75°. One of the fields has a magnitude of√2 x 10^-2 T. The dipole attains stable equilibrium at an angle of 30° with this field. What is the magnitude of the other field?

A
0.01 T

B
0.02 T

C
0.03 T

D
0.04 T

Solution
Question 9
1 / -0

A steel wire of length 'l' has a magnetic moment M. It is bent into a semicircular arc. The new magnetic moment is

A
M

B
2M/π

C
M/π

D
Mπ

Solution
Question 10
1 / -0

A bar magnet of magnetic moment 2.0 JT^-1 lies aligned with the direction of a uniform magnetic field of 0.25 T. What is the work done to turn the magnet so as to align its magnetic moment opposite to the field direction?

A
0.25 J

B
0.5 J

C
0.75 J

D
1.0 J

Solution
Question 11
1 / -0

Directions: From the statements of Assertion and Reason mark the correct answer from the options.
(a) If both assertion and reason are true, and reason is the correct explanation of assertion.
(b) If both assertion and reason are true, but reason is not the correct explanation of assertion.
(c) If assertion is true, but reason is false.
(d) If both assertion and reason are false.
Assertion: Diamagnetic materials can exhibit magnetism.
Reason: Diamagnetic materials have permanent magnetic dipole moment.

A
(a)

B
(b)

C
(c)

D
(d)

Solution

Some materials when placed in an external magnetic field, acquire a very low magnetism in a direction opposite to the field. These materials when brought near the end of a strong magnet, they get repelled. These materials are diamagnetic and this property of materials is called the diamagnetism. This property is generally found in materials in which there are even number of electrons in their atoms (or molecules) and pairs are formed with two electrons. In each pair, the spin of one electron is in direction opposite to the spin of other electron. Hence, the electrons of each pair completely cancel the magnetic moment of each other. Thus, the net magnetic moment of each atom of such material is zero. Hence, option (c) is true.
Question 12
1 / -0

A magnet of magnetic moment M and length 2l is bent at its mid-point such that the angle of bending is 60^o. Now, the magnetic moment is

A
M

B
2M

C
M/2

D
M/√2

Solution
Question 13
1 / -0

A toy of mass M₁ is pulled along a horizontal frictionless surface by rope of mass M₂. A force F is applied to the free end of the rope. the force exerted on the toy is:

A
F

B
M₁F/(M₁ + M₂)

C
M₁F/(M₁ - M₂)

D
M₂F/(M₁ + M₂)

Solution

a = F/(M₁ + M₂)
force on mass M₁ = M₁ × a = M₁F/(M₁+ M₂)
Question 14
1 / -0

A long horizontal rod has a bead, which can slide along its length and is initially placed at a distance L from one end A of the rod. The rod is set in angular motion about A with constant angular acceleration α . If the coefficient of friction between the rod and the bead is and gravity is neglected, then the time after which the bead starts slipping is

A

B

C

D
infinitesimal

Solution
Question 15
1 / -0

Two weights 'w₁' and 'w₂' are suspended by two strings on a frictionless pulley. When the pulley is pulled up with an acceleration 'g', then the tension in the string is

A

B

C

D

Solution

Let m₁ > m₂.
As the lift is accelerating with acceleration (a = g), then the tension in the string is