Atoms — Physics STD 12 Science — Question

Consider a current carrying wire (current I) in the shape of a circle.

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:

A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from the slit. if the speed of the electrons is increased , which of the following statements is correct?

A rocket is going towards moon with a speed v. The astronaut in the rocket sends signals of frequency v  towards the moon and receives them back on reflection from the moon. What will be the frequency of the signal received by the astronaut (Take v << c)

(a)

(b)

(c)

(d)

An electron is travelling horizontally towards east. A magnetic field in vertically downward direction exerts a force on the electron along

(a) East

(b) West

(c) North

(d) South

In a Millikan's oil drop experiment the charge on an oil drop is calculated to be 6.35 . The number of excess electrons on the drop is

(a) 3.9

(b) 4

(c) 4.2

(d) 6

If a magnetic substance is kept in a magnetic field, then which of the following is thrown out

(a) Paramagnetic

(b) Ferromagnetic

(c) Diamagnetic

(d) Antiferromagnetic

If the speed of light in vacuum is C m/sec, then the velocity of light in a medium of refractive index 1.5

(a) Is 1.5 × C	(b) Is C
(c) Is	(d) Can have any velocity

In the given figure, when galvanometer shows no deflection, the current (in ampere) flowing through 5Ω  resistance will be

(a) 0.5

(b) 0.6

(c) 0.9

(d) 1.5

An electron revolves 6 × 10¹⁵ times/sec in circular loop.  The current in the loop is

(a) 0.96 mA

(b) 0.96 m A

(c) 28.8 A

(d) None of these