Wave Optics — Physics STD 12 Science — Question

When a wire loop is rotated in a magnetic field, the direction of induced e.m.f. changes once in each

(a)  revolution

(b)  revolution

(c) 1 revolution

(d) 2 revolution

A small bar magnet A oscillates in a horizontal plane with a period T at a place where the angle of dip is 60^o. When the same needle is made to oscillate in a vertical plane coinciding with the magnetic meridian, its period will be

(a)

(b) T

(c)

(d) 2T

The current flowing in a copper voltameter is 3.2 A. The number of copper ions ( deposited at the cathode per minute is

(a) 0.5

(b) 1.5

(c) 3

(d) 6

Electromagnetic waves are transverse in nature is evident by

(a) Polarization

(b) Interference

(c) Reflection

(d) Diffraction

Solve the previous question if the closed loop is completely enclosed in the circuit containing the switch.

1. An anticlockwise current-pulse.
2. A clockwise current-pulse.
3. An anticlockwise current-pulse and then a clockwise current-pulse.
4. A clockwise current-pulse and then an anticlockwise current-pulse.

The electric flux for Gaussian surface A that enclose the charged particles in free space is (given q₁ = –14 nC, q₂ = 78.85 nC, q₃ = – 56 nC)

(a) 103 Nm2 C–1

(b) 103 CN-1 m–2

(c) 6.32 × 103 Nm2 C–1

(d) 6.32 × 103 CN-1 m–2

Which statement is correct

(a) N-type germanium is negatively charged and P-type germanium is positively charged

(b) Both N-type and P-type germanium are neutral

(c) N-type germanium is positively charged and P-type germanium is negatively charged

(d) Both N-type and P-type germanium are negatively charged

When there is an electric current through a conducting wire along its length, then an electric field must exist

(a)  Outside the wire but normal to it	(b) Outside the wire but parallel to it
(c) Inside the wire but parallel to it	(d) Inside the wire but normal to it

Each plate of a parallel plate capacitor has a charge q on it. The capacitor is now connected to a batter. Now:

1. The facing surfaces of the capacitor have equal and opposite charges.
2. The two plates of the capacitor have equal and opposite charges.
3. The battery supplies equal and opposite charges to the two plates.
4. The outer surfaces of the plates have equal charges.

Suppose we consider a large number of containers each containing initially 10000 atoms of a radioactive material with a half life of 1 year. After 1 year: