In a series L-C-R circuit, resistance R = 10 Ω and the impedance Z = 10 Ω. The phase difference between the current and the voltage is
0o
30o
45o
60o
The impedance of a circuit, when a resistance R and an inductor of inductance L are connected in series in an AC circuit of frequency f, is
A choke is preferred to a resistance for limiting current in AC circuit because
choke is cheap
there is no wastage of power
choke is compact in size
choke is a good absorber of heat
B.
there is no wastage of power
In an AC circuit, the coil of high inductance and negligible resistance used to control current, is called the choke coil. The power factor of such a coil is given by
cos =
≈ ...( as R<< ωL )
As R << ωL, cos is very small.
Thus, the power absorbed by the coil is very small. The only loss of energy is due to hysteresis in the iron core, which is much less than the loss of energy in the resistance that can also reduce the current if placed instead of the choke coil.
Induced emf in the coil depends upon
conductivity of coil
amount of flux
rate of change of linked flux
resistance of coil
In an L-C-R circuit inductance is changed from L to L/2.To keep the same resonance frequency, C should be changed to
2 C
4 C
220 V, 50 Hz, AC source is connected to an inductance of 0.2 Hand a resistance of 20 Ω in series. Whatis the current in the circuit?
3.33 A
33.3 A
5 A
10 A
If we change the value of R, then
voltage does not change on L
voltage does not change on LC combination
voltage does not change on C
voltage changes on LC combination
Real power consumption in a circuit is least when it contains.
high R, low L
high R, high L
low R, high L
high R, low C
An inductor (L = 20 H), a resistor (R = 100 Ω) and a battery (E = 10 V) are connected in series. After a long time, the circuit is short-circuited and then the battery is disconnected. Find the current in the circuit at 1 ms after short circuiting.
4.5 x 105 A
3.2x 10-5 A
9.8 × 10-5 A
6.7 × 10-4 A