A galvanometer has a resistance of 30 Q. It gives full scale deflection with a current of 2mA. Calculate, the value of the resistance needed to convert it into an ammeter of range 0 − 0.3 A. The value of the resistance needed to convert galvanometer into ammeter
0.2 Ω
0.3 Ω
0.4 Ω
0.52 Ω
The given circuit diagram shows a series L-C-R circuit connected to a variable frequency 230 V, source: L =5.0 H, C = 80 µF, R = 40 Ω
The frequency and impedance of the circuit at the resonating frequency are
50 rad/s and 5.75 A
1000 rad/s and 3 A
10 rad/s and 2 A
20 rad/s and 4 A
The instantaneous current and voltage of an AC circuit are given by I= 10 sin 300t A and V = 200 sin 300t V. The power dissipation in the circuit is
500 W
2000 W
1000 W
100 W
In a series L-C-R circuit, the voltages across an inductor, a capacitor and a resistor are 30V, 30V and 60 V respectively. The phase difference between the applied voltage and the current in the circuit is
O°
90°
30°
60°
An AC source, of voltage V =Vm sin ωt, is applied across a series RC circuit in which the capacitive impedance is 'a' times the resistance in the circuit. The value of the power factor of the circuit is
O
None of these
B.
Since, capacitive impedance is 'a' times the resistance in the RC series AC circuit.
Therefore, Z2 = R2 + XC2
According to the question
XC = aR
Therefore, Z2 = R2 + a2R2
Z =
Power factor cos = R/Z = 1/
Current in a circuit falls steadily from 2.0 A to 0.0 A in 10 ms. If an average emf of 200 V is induced, then the self-inductance of the circuit is
1 H
2 H
1/2 H
2 H
A rectangular coil of area A, having number of turns N is rotated at f revolutions per second in a uniform magnetic field B. The maximum emf induced in the coil is
fNB
2fNBA
fBA
fNBA
The polarity of the capacitor in the situation described by Fig.
Plate A and plate B both positive
Plate A negative and plate B positive
Plate A positive and plate B negative
Plate A and plate B both negative
A step down transformer operated on a 2.5 kV line. It supplies a load with 20 A. The ratio of the primary winding to the secondary is 10 : 1. If the transformer is 90% efficient, the power output is
4.5 X 104 W
4.5 × 102 W
6 x 104 W
6 X 104 w
A step down transformer operated on a 2.5 kV line. It supplies a load with 20 A. The ratio of the primary winding to the secondary is 10 : 1. If the transformer is 90% efficient, the voltage in the secondary is
225 V
550 V
250 V
200 V