41.

A and B are two points on a uniform ring of resistance R. The ∠ ACB = 0, where C is the centre of the ring. The equivalent resistance between A and B is

• 

• 

• 

• 

A square loop ABCD, carrying a current I₂, is placed near and coplanar with a long straight conductor XY carrying a current I₁, as shown in figure. The net force on the loop will be

• $\frac{{\mathrm{\mu }}_0 {\mathrm{I}}_1 {\mathrm{I}}_2}{2 \mathrm{\pi }}$

• $\frac{{\mathrm{\mu }}_0 {\mathrm{I}}_1{\mathrm{I}}_2 \mathrm{L}}{2 \mathrm{\pi }}$

• $\frac{2 {\mathrm{\mu }}_0 {\mathrm{I}}_1{\mathrm{I}}_2 \mathrm{L}}{3 \mathrm{\pi }}$

• $\frac{2{\mathrm{\mu }}_0 {\mathrm{I}}_1 {\mathrm{I}}_2}{3 \mathrm{\pi }}$

A circular coil of radius 10 cm, 500 turns and resistance 2 Ω is placed with its plane perpendicular to the horizontal component of the earth's magnetic field. It is rotated about its vertical diameter through 180° in 0.25 s. The
current induced in the coil is

(Horizontal component of the earth's magnetic field at that place is 3.0 x 10^-5 T)

• 1.9 × 10^-3 A

• 2.9 × 10^-3 A

• 3.9 × 10^-3 A

• 4.9 × 10^-3 A

A parallel plate capacitor with air as a dielectric has capacitance C. A slab of dielectric constant K, having same thickness as the separation between the plates is introduced so as to fill one-fourth of the capacitor as shown in the figure. The new capacitance will be

• $\left(\mathrm{K} + 3\right) \frac{\mathrm{C}}{4}$

• $\left( \mathrm{K} + 2 \right) \frac{\mathrm{C}}{4}$

• $\left(\mathrm{K} + 1\right) \frac{\mathrm{C}}{4}$

• $\frac{\mathrm{K} \mathrm{C}}{4}$

In the circuit shown in figure, if A the diode forward voltage is 0.3 V, the voltage difference between A and B is

• 1.3 V

• 2.3 V

• 0

• 0.5 V

Assertion:  Acceleration of charged particle in non-uniform electric field does not depend on velocity of charged particle.

Reason: Charge is an invariant quantity. That is amount of charge on particle does not depend on frame of reference.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion:  If a dielectric is placed in external field then field inside dielectric will be less than applied field.

Reason:  Electric field will induce dipole moment opposite to field direction.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion:  An electrical bulb starts glowing instantly as it is switched on. 

Reason:  Drift speed of electrons in a metallic wire is very large.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false

A 2.0 cm tall object is placed 15 cm in front of a concave mirror of focal length 10 cm. What is the size and nature of the image?

• 4 cm, real

• 4 cm, virtual

• 1.0 cm, real 

• none of these

The least distance of vision of a longsighted person is 60 cm. By using a spectacle lens, this distance is reduced to 12 cm. The power of the lens is

• + 0.5 D

• + ( 20/30 ) D

• $-$ (10/3) D

• + 2.0 D