Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

Which of the following is an example of a molecule whose centre of mass of positive and negative charges coincide each other?

Suppose, the electron in a hydrogen atom makes transition from n = 3 to n = 2 in 10^-8s. The order of the torque acting on the electron in this period, using the relation between torque and angular momentum as discussed in the chapter on rotational mechanics is:

If the flux of the electric field through a closed surface is zero, then:

Which of the following graphs shows the variation of magnetic induction B with distance r from a long wire carrying current

(a)

(b)

(c)

(d)

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

A heavy stone is thrown in from a cliff of height h in a given direction. The speed with which it hits the ground:

1. Must depend on the speed of projection.
2. Must be larger than the speed of projectio.
3. Must be independent of the speed of projection.
4. May be smaller than the speed of projection.

Before the saturation state of a diode at the plate voltages of 400 V and 200 V respectively the currents are i₁ and i₂ respectively. The ratio i₁/i₂ will be

(a)

(b) 2

(c) 2

(d) 1/2

A long straight wire carries a current of π amp. The magnetic field due to it will be 5  at what distance from the wire [ permeability of air]

(a)   metre

(b)  metre

(c)  metre

(d)  metre

Huygens' principle of secondary wavelets may be used to:

The refractive indices of glass and water w.r.t. air are 3/2 and 4/3 respectively. The refractive index of glass w.r.t. water will be

(a) 8/9

(b) 9/8

(c) 7/6

(d) None of these