Moving Charges and Magnetism — Physics STD 12 Science — Question

A particle of mass 'm' and charge 'q' enters in an uniform magnetic field B perpendicularly. The radius of its path will be :

The emf of a thermocouple, one junction of which is kept at 0℃, is given by  the Peltier co-efficient will be

(a) (t + 273) (a + 2bt)	(b) (t + 273) (a – 2bt)
(c) (t – 273) (a- 2bt)	(d) (t – 273) (a – 2bt)

The figure shows three circuits with identical batteries, inductors, and resistors. Rank the circuits according to the current through the battery (i) just after the switch is closed and (ii) a long time later, greatest first

(a) (i)  (ii)

(b) (i)   (ii)

(c) (i)  (ii)

(d) (i)  (ii)

The diagram below shows two coils A and B placed parallel to each other at a very small distance. Coil A is connected to an ac supply. G is a very sensitive galvanometer. When the key is closed

(a) Constant deflection will be observed in the galvanometer for 50 Hz supply

(b) Visible small variations will be observed in the galvanometer for 50 Hz input

(c) Oscillations in the galvanometer may be observed when the input ac voltage has a frequency of 1 to 2 Hz

(d) No variation will be observed in the galvanometer even when the input ac voltage is 1 or 2 Hz

Pick out the electromagnetic wave which is highly harmful to humans.

Variation of current and voltage in a conductor has been shown in the diagram below. The resistance of the conductor is

(a) 4 ohm

(b) 2 ohm

(c) 3 ohm

(d) 1 ohm

The magnetic field B with in the solenoid having n turns per metre length and carrying a current of i ampere is given by

(a)

(b)

(c) 4π

(d) ni

A point charge is kept at the centre of a metallic insulated spherical shell. Then

(a) Electric field out side the sphere is zero	(b) Electric field inside the sphere is zero
(c) Net induced charge on the sphere is zero	(d) Electric potential inside the sphere is zero

The distance of two points on the axis of a magnet from its centre is 10 cm and 20 cm respectively. The ratio of magnetic intensity at these points is 12.5 : 1. The length of the magnet will be

(a) 5 cm

(b) 25 cm

(c) 10 cm

(d) 20 cm

A body can be negatively charged by

(a) Giving excess of electrons to it	(b) Removing some electrons from it
(c) Giving some protons to it	(d) Removing some neutrons from it