Electromagnetic Induction — Physics STD 12 Science — Question

If the two ends of a p-n junction are joined by a wire:

1. There will not be a steady current in the circuit.
2. There will be a steady current from the n-side to the p-side.
3. There 'will a steady current from the p-side. to the n-side.
4. There may or may not be a current depending upon the resistance of the connecting wire.

A proton and a deutron both having the same kinetic energy, enter perpendicularly into a uniform magnetic field B. For motion of proton and deutron on circular path of radius   and   respectively, the correct statement is

(a)

(b)

(c)

(d)

 and  represent mass of neutron and proton respectively. If an element having atomic mass M has N-neutron and Z-proton, then the correct relation will be

(a)

(b)

(c)

(d)

An electrical cable of copper has just one wire of radius 9mm. Its resistance is 5 ohm. This single copper wire of the cable is replaced by 6 different well insulated copper wires each of radius 3mm. The total resistance of the cable will now be equal to:

If an electron jumps from 1st orbital to 3rd orbital, then it will

(a) Absorb energy	(b) Release energy
(c) No gain of energy	(d) None of these

Assertion :   Penetrating power of X-rays increases with the increasing the wavelength.

Reason    : The penetrating power of X-rays increases with the frequency of X-rays.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If assertion is false but reason is true.

An electric current i enters and leaves a uniform circular wire of radius a through diametrically opposite points. A charged particle q moving along the axis of the circular wire passes through its centre at speed v. The magnetic force acting on the particle when it passes through the centre has a magnitude:

The contact force exerted by a body A on another body B is equal to the normal force between the bodies. We conclude that:

1. The surfaces must be frictionless.
2. The force of friction between the bodies is zero.
3. The magnitude of normal force equals that of friction.
4. The bodies may be rough but they don't slip on each other.

Which among the following is an example of a semiconductor?

A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are joined together.  The power of the combination will be

(a) – 16 D

(b) + 16 D

(c) – 6 D

(d) + 6 D