Electric Charges and Fields — Physics STD 12 Science — Question

Three bulbs of 40 W, 60 W, 100 W are arranged in series with 220 volt supply which bulb has minimum resistance

(a) 100 W

(b) 40 W

(c) 60 W

(d) Equal in all bulbs

The contribution in the total current flowing through a semiconductor due to electrons and holes are   and   respectively. If the drift velocity of electrons is   times that of holes at this temperature, then the ratio of concentration of electrons and holes is

(a) 6 : 5

(b) 5 : 6

(c) 3 : 2

(d) 2 : 3

For making standard resistance, wire of following material is used:

An electric dipole will experience a net force when it is placed in.

A straight copper wire is moved in a uniform magnetic field such that it cuts the magnetic lines of force. Then

In a photocell bichromatic light of wavelength 2475 Å and 6000 Å are incident on cathode whose work function is 4.8 eV. If a uniform magnetic field of 3 × 10^–5 Tesla exists parallel to the plate, the radius of the path describe by the photoelectron will be (mass of electron = 9 × 10^–31 kg)

(a) 1 cm

(b) 5 cm

(c) 10 cm

(d) 25 cm

50% of the X-ray coming from a Coolidge tube is able to pass through a 0.1mm thick aluminium foil. The potential difference between the target and the filament is increased. The thickness of the aluminium foil that will allow 50% of the X-ray to pass through will be:

The diffusion current in a p-n junction is:

1. From the n-side to the p-side.
2. From the p-side to the n-side.
3. From the n-side to the p-side if the junction is forward-biased and in the opposite direction if it is reverse-biased.
4. From the p-side to the n-side if the junction is forward-biased and in the opposite direction if it is reverse-biased.

A polaroid is placed at 45^o to an incoming light of intensity . Now the intensity of light passing through polaroid after polarisation would be

(a)

(b)

(c)

(d) Zero

A susceptibility of a certain magnetic material is 400. What is the class of the magnetic material?