Electric Charges and Fields — Physics STD 12 Science — Question

The electric flux on a Gaussian spherical surface of radius 15 cm, drawn with a point charge as the centre, is ф. If the radius of this surface is tripled, then the electric flux passing through the surface will be:

Polarised glass is used in sun glasses because

(a) It reduces the light intensity to half an account of polarisation

(b) It is fashionable

(c) It has good colour

(d) It is cheaper

The breakdown in a reverse biased p-n junction diode is more likely to occur due to.

The magnetic induction at a point P which is distant 4 cm from a long current carrying wire is . The field of induction at a distance 12 cm from the same current would be

(a) 3.33

(b) 1.11

(c) 3

(d) 9

The main cause of Zener breakdown is:

Which experiment seemed to make it clear that light propogates as a wave?

Resistance in the two gaps of a meter bridge are 10 ohm and 30 ohm respectively. If the resistances are interchanged the balance point shifts by

(a) 33.3 cm

(b) 66.67cm

(c) 25 cm

(d) 50 cm

A proton and an α -  particle enter a uniform magnetic field perpendicularly with the same speed. If proton takes 25 μ  sec to make 5 revolutions, then the periodic time for the α -  particle would be

(a) 50 μ  sec

(b) 25 μ sec

(c) 10 μ  sec

(d) 5 μ  sec

Three identical adiabatic containers A, B and C contain helium, neon and oxygen respectively at equal pressure. The gases are pushed to half their original volumes.

1. The final temperatures in the three containers will be the same.
2. The final pressures in the three containers will be the same.
3. The pressures of helium and neon will be the same but that of oxygen will be different.
4. The temperatures of helium and neon will be the same but that of oxygen will be different.

In a stationary wave,

1. All the particles of the medium vibrate in phase.
2. All the antinodes vibrate in phase.
3. The alternate antinodes vibrate in phase.
4. All the particles between consecutive nodes vibrate in phase.