Electric Charges and Fields — Physics STD 12 Science — Question

A sphere is rotating about a diameter:

1. The particles on the surface of the sphere do not have any linear acceleration.
2. The particles on the diameter mentioned above do not have any linear acceleration.
3. Different particles on the surface have different angular speeds.
4. All the particles on the surface have same linear speed.

A proton enters a magnetic field of flux density 1.5   with a velocity of  2   at an angle of 30°  with the field. The force on the proton will be

(a) 2.4

(b) 0.24

(c) 24

(d) 0.024

The figure represents the observed intensity of X-rays emitted by an X-ray tube as a function of wavelength. The sharp peaks A and B denote

(a) Band spectrum	(b) Continuous spectrum
(c) Characteristic radiations	(d) White radiations

A coil having n turns and resistance R W  is connected with a galvanometer of resistance 4RΩ. This combination is moved in time t seconds from a magnetic field W₁ weber to W₂ weber. The induced current in the circuit is

(a)

(b)

(c)

(d)

The variation of wavelength λ  of the   line with atomic number Z of the target is shown by the following curve of

(a) A

(b) B

(c) C

(d) None of these

Two sources give interference pattern which is observed on a screen, D distance apart from the sources. The fringe width is 2w. If the distance D is now doubled, the fringe width will

(a) Become w/2

(b) Remain the same

(c) Become w

(d) Become 4w

When an atomic gas or vapour is excited at low pressure, by passing an electric current through it then?

Conventional flow of current will always be from:

In Milikan's oil drop experiment, a charged drop falls with terminal velocity V. If an electric field E is applied in vertically upward direction then it starts moving in upward direction with terminal velocity 2V. If magnitude of electric field is decreased to , then terminal velocity will become

(a)

(b) V

(c)

(d) 2V