Ac Generator

Question 1

Define alternating current

Answer 1

Alternating current is the one which changes in magnitude continuously and in direction periodically. The maximum value of current is called current-amplitude or peak value of current.

Question 2

Reactance

Answer 2

The opposition offered by inductance and capacitance or both in ac circuit is called reactance. It is denoted by Xc or XL.
The opposition due to inductor alone is called the inductive reactance while that due to capacitance alone is called the capacitive reactance.

Question 3

Purely Resistive Circuit

Answer 3

If a circuit contains pure resistance, then phase difference =0 i.e., current and voltage are in the same phase.

Impedance, Z = R

Question 4

Purely Capacitive Circuit

Answer 4

If circuit contains pure capacitance, then
Phi =90
, i.e., current leads the applied voltage by angle
90

Question 5

Series LCR Circuit

Answer 5

If a circuit contains inductance L, capacitance C and resistance R,
connected in series to an alternating voltage V = Vo sin a

Question 6

Resonant Circuits

Answer 6

Series CR circuit: In series LCR circuit, when phase (Ф) between current and voltage is zero, the circuit is said to be
resonant circuit.

Question 7

Quality factor (Q)

Answer 7

The quality factor (Q) of series LCR circuit is defined as the ratio of the resonant frequency to frequency band width of the resonant curve.

Question 8

Power factor

Answer 8

Cos phi = R/Z

Question 9

Max power

Answer 9

Cos phi=1
Z=R

Question 10

Min power

Answer 10

Cos phi=0
R=0

Question 11

Wattless current

Answer 11

In purely inductive or purely capacitive circuit, power loss is zero. In such a circuit, current flowing is called wattless current.

Question 12

Ac generator

Answer 12

• It is a device used to convert mechanical energy into electrical energy and is based on the phenomenon of electromagnetic induction.
• If a coil of N turns, area A is rotated at frequency v in uniform magnetic field of induction B, then motional emf in coil (if initially it is perpendicular to field) is

Question 13

Transformer

Answer 13

• A transformer is a device which converts low ac voltage into high ac voltage and vice versa.
• It works on the principle of mutual induction.
• If Np and Ny are the number of turns in primary and secondary coils, Vp and Ip are voltage and current in primary coil, then voltage (Vs) and current (Is) in secondary coil will be