Nuclei — Physics STD 12 Science — Question

When the P end of P-N junction is connected to the negative terminal of the battery and the N end to the positive terminal of the battery, then the P-N junction behaves like           (a) A conductor(b) An insulator(c) A super-conductor(d) A semi-conductor

Consider an extended object immersed in water contained in a plane trough. When seen from close to the edge of the trough the object looks distorted because:

The magnetic field of the earth can be modelled by that of a point dipole placed at the centre of the earth. The dipole axis makes an angle of 11.3° with the axis of the earth. At Mumbai, declination is nearly zero. Then,

A long, straight wire carries a current i. The magnetizing field intensity H is measured at a point P close to the wire. A long, cylindrical iron rod is brought close to the wire so that the point P is at the centre the rod. The value of H at P will:

1. Increase many times.
2. Decrease many times
3. Remain almost constant.
4. Become zero.

Which of the following statement is not true?

Ampere’s circuital law is equivalent to:

In a transistor, a change of 8.0 mA in the emitter current produces a change of 7.8 mA in the collector current. What change in the base current is necessary to produce the same change in the collector current(a) 50 mA(b) 100 mA(c) 150 mA(d) 200 mA