Electric Charges and Fields — Physics STD 12 Science — Question

In case of NPN-transistors the collector current is always less than the emitter current because(a) Collector side is reverse biased and emitter side is forward biased(b) After electrons are lost in the base and only remaining ones reach the collector(c) Collector side is forward biased and emitter side is reverse biased(d) Collector being reverse biased attracts less electrons

In what form is energy present in the capacitor?

In an area of constant magnetic field, a charged particle enters in a direction parallel to the direction of magnetic field with its velocity. The speed of particle is:

The electric power :

The time constant of an LR circuit represents the time in which the current in the circuit(a) Reaches a value equal to about 37% of its final value(b) Reaches a value equal to about 63% of its final value (c) Attains a constant value(d) Attains 50% of the constant value

An electric dipole placed in a non-uniform electric field can experience

Assertion :  An electron and proton enters a magnetic field with equal velocities, then, the force experienced by the proton will be more than electron.
Reason     : The mass of proton is 1837 times more than electron.(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.

Coating of strontium oxide on Tungsten cathode in a valve is good for thermionic emission because(a) Work function decreases(b) Work function increases(c) Conductivity of cathode increases(d) Cathode can be heated to high temperature

A transformer increases ac voltage supply from 220 V to 2200 V. If there are 2000 turns in the second- ary coil, then number of turns in the primary coil is: