Electric Charges and Fields — Physics STD 12 Science — Question

In a PNP transistor working as a common-base amplifier, current gain is 0.96 and emitter current is 7.2 mA. The base current is(a) 0.4 mA(b) 0.2 mA(c) 0.29 mA(d) 0.35 mA

A horizontal circular loop carries a current that looks clockwise when viewed from above. It is replaced by an equivalent magnetic dipole consisting of a south pole S and a north pole N:

1. The line SN should be along a diameter of the loop.
2. The line SN should be perpendicular to the plane of the loop.
3. The south pole should be slow the loop.
4. The north pole should be below the loop.

Coherent sources are those sources for which(a) Phase difference remain constant (b) Frequency remains constant(c) Both phase difference and frequency remains constant(d) None of these

An electric kettle has two heating coils. When one coil is used, water in the kettle boils in 5 minutes, while when second coil is used, same water boils in 10 minutes. If the two coils, connected in parallel are used simultaneously, the same water will boil in time(a) 3 min 20 sec(b) 5 min(c) 7 min 30 sec(d) 2 min 30 sec

The force with which a magnet attracts objects like iron is called ....................... .

Force between two unit pole strength placed at a distance of one metre is

The relaxation time in conductors(a) Increases with the increase of temperature(b) Decreases with the increase of temperature(c) It does not depend on temperature(d) All of sudden changes at 400 K

Consider an NPN transistor amplifier in common-emitter configuration. The current gain of the transistor is 100. If the collector current changes by 1 mA, what will be the change in emitter current(a) 1.1 mA(b) 1.01 mA (c) 0.01 mA(d) 10 mA