Current Electricity — Physics STD 12 Science — Question

What is the unit of surface charge density in the SI unit?

A charged particle of mass 5   is held stationary in space by placing it in an electric field of strength   directed vertically downwards. The charge on the particle is

(a) -20

(b) -5

(c) 5

(d) 20

Additivity of the electric charges means that the total charge of a system is the _____ of all individual charges in the system.

There is a current of 20 amperes in a copper wire of  square metre area of cross-section. If the number of free electrons per cubic metre is , then the drift velocity is

(a) 125

(b) 12.5

(c) 1.25

(d) 1.25

When the light source is kept 20 cm away from a photo cell, stopping potential 0.6 V is obtained. When source is kept 40 cm away, the stopping potential will be

(a) 0.3 V

(b) 0.6 V

(c) 1.2 V

(d) 2.4 V

The shortest wavelength in the Lyman series of hydrogen spectrum is 912 Å corresponding to a photon energy of 13.6 eV. The shortest wavelength in the Balmer series is about

(a) 3648 Å

(b) 8208 Å

(c) 1228 Å

(d) 6566 Å

When charged particle enters-a uniform magnetic field, its K.E:

The shape of the wavefront of the portion of the wavefront of light from a distant star intercepted by the earth is

A negatively charged plate has charge density of 2 . The initial distance of an electron which is moving toward plate, cannot strike the plate, if it is having energy of 200 eV

(a) 1.77 mm

(b) 3.51 mm

(c) 1.77 cm

(d) 3.51 cm