Communication System — Physics STD 12 Science — Question

Assertion :   The induced emf in a conducting loop of wire will be non zero when it rotates in a uniform magnetic field.

Reason    : The emf is induced due to change in magnetic flux.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Heat produced in a wire of resistance R due to current flowing at constant potential difference is proportional to

(a)

(b)

(c) R

(d)

What will be the nature of charge on the metal paper clip of electroscope when a negatively charged body is brought in contact with it?

1 Coulomb = ________ Electro Static Unit.

If the distance between H and Cl in HCl molecule is 1.28 A, then the value of electric dipole moment of this molecule will be (in Coulomb-meter):

The electromagnetic waves of frequency 2 MHz to 30 MHz are

(a) In ground wave propagation	(b) In sky wave propagation
(c) In microwave propagation	(d) In satellite communication

In the adjoining diagram, a wavefront AB, moving in air is incident on a plane glass surface XY. Its position CD after refraction through a glass slab is shown also along with the normals drawn at A and D. The refractive index of glass with respect to air (μ = 1) will be equal to

(a)

(b)

(c)

(d)

A rectangular loop carrying a current i is situated near a long straight wire such that the wire is parallel to the one of the sides of the loop and is in the plane of the loop. If a steady current I is established in wire as shown in figure, the loop will

(a) Rotate about an axis parallel to the wire

(b) Move away from the wire or towards right

(c) Move towards the wire

(d) Remain stationary

If a charged particle kept at rest experiences an electromagnetic force:

1. The electric field must not be zero.
2. The magnetic field must not be zero.
3. The electric field may or may not be zero.
4. The magnetic field may or may not be zero.