Science (English Medium) Class 12 - CBSE Question Bank Solutions for Physics

In n-type semiconductor majority carriers and minority carriers are respectively ______.

In p-type semiconductor, the dopant is ______.

In p-type semiconductor, ______.

The electron and hole concentration in a semiconductor in thermal equilibrium is given by ______.

The electric potential at a point on the equatorial line of an electric dipole is ______.

A hollow metal sphere of radius 5 cm is charged such that the potential on its surface is 10 V. The potential at a distance of 2 cm from the centre of the sphere is ______.

A.C. power is transmitted from a power house at a high voltage as ______.

When an ac voltage of 220 V is applied to the capacitor C, then ______.

A capacitor has capacitance C and reactance X, if capacitance and frequency become double, then reactance will be ______.

A sinusoidal voltage of peak value 283 V and frequency 50 Hz is applied to a series LCR circuit in which R = 3 Ω, L = 25.48 mH, and C = 796 µF, then the power dissipated at the resonant condition will be ______.

In a pure semiconductor crystal of Si, if antimony is added then what type of extrinsic semiconductor is obtained. Draw the energy band diagram of this extrinsic semiconductor so formed.

Is the momentum conserved when charge crosses a junction in an electric circuit? Why or why not?

The relaxation time τ is nearly independent of applied E field whereas it changes significantly with temperature T. First fact is (in part) responsible for Ohm’s law whereas the second fact leads to variation of ρ with temperature. Elaborate why?

1. Consider circuit in figure. How much energy is absorbed by electrons from the initial state of no current (ignore thermal motion) to the state of drift velocity?
2. Electrons give up energy at the rate of RI² per second to the thermal energy. What time scale would one associate with energy in problem (a)? n = no of electron/volume = 10²⁹/m³, length of circuit = 10 cm, cross-section = A = (1mm)²

When an AC voltage of 220 V is applied to the capacitor C ______.

1. the maximum voltage between plates is 220 V.
2. the current is in phase with the applied voltage.
3. the charge on the plates is in phase with the applied voltage.
4. power delivered to the capacitor is zero.

A device ‘X’ is connected to an a.c source. The variation of voltage, current and power in one complete cycle is shown in figure.

1. Which curve shows power consumption over a full cycle?
2. What is the average power consumption over a cycle?
3. Identify the device ‘X’.