Current Electricity — Physics STD 12 Science — Question

What is shape of magnet in moving coil galvanometer to make the radial magnetic field

(a) Concave

(b) Horse shoe magnet

(c) Convex

(d) None of these

The focal length of the objective of a compound microscope if f_o and its distance from the eyepiece is L. The object is placed at a distance u from the objective. For proper working of the instrument:

1. L < u
2. L > u
3. f_o < L < 2f_o
4. L > 2f_o

You are given several identical resistances each of value R = 10 Ω  and each capable of carrying maximum current of 1 ampere. It is required to make a suitable combination of these resistances to produce a resistance of  5 Ω which can carry a current of 4 amperes. The minimum number of resistances of the type R that will be required for this job

(a) 4

(b) 10

(c) 8

(d) 20

In a Young's double slit experiment, the fringe width will remain same, if (D = distance between screen and plane of slits, d = separation between two slits and λ =  wavelength of light used)

(a) Both λ and D are doubled	(b) Both d and D are doubled
(c) D is doubled but d is halved	(d) λ  is doubled but d is halved

What is the use of a Van de Graff generator?

In an ideal parallel LC circuit, the capacitor is charged by connecting it to a D.C. source which is then disconnected. The current in the circuit.

In the process of fission, the binding energy per nucleon:

In N-type semiconductors, majority charge carriers are

(a) Holes

(b) Protons

(c) Neutrons

(d) Electrons

Two positive point charges of 12 μC  and 8 μC  are 10cm apart. The work done in bringing them 4 cm closer is

(a) 5.8 J

(b) 5.8 eV

(c) 13 J

(d) 13 eV

A charge Q is uniformly distributed over a large plastic plate. The electric field at a point P close to the centre of the plate is 10Vm^-1. If the plastic plate is replaced by a copper plate of the same geometrical dimensions and carrying the same charge Q, the electric field at the point P will become: