When the speed of a dc motor increases the armature current
1. Increases
2. Decreases
3. Does not change
4. Increases and decreases continuously
An electric motor operating on a 60 V dc supply draws a current of 10 A. If the efficiency of the motor is 50%, the resistance of its winding is
1. 3Ω
2. 6Ω
3. 15Ω
4. 30Ω
The potential difference V and the current i flowing through an instrument in an ac circuit of frequency f are given by volts and I = 2 sin ωt amperes (where ω = 2πf). The power dissipated in the instrument is
1. Zero
2. 10 W
3. 5 W
4. 2.5 W
In an ac circuit, V and I are given by V = 100 sin (100 t) volts, . The power dissipated in circuit is
1. 104 watt
2. 10 watt
3. 2.5 watt
4. 5 watt
The impedance of a coil, when DC supply is replaced by AC supply:
1. will remain the same
2. will increase
3. will decrease
4. will be zero
A generator produces a voltage that is given by V = 240 sin 120 t, where t is in seconds. The frequency and r.m.s. voltage are
1. 60 Hz and 240 V
2. 19 Hz and 120 V
3. 19 Hz and 170 V
4. 754 Hz and 70 V
The peak value of an alternating e.m.f. E is given by is 10 volts and its frequency is 50 Hz. At time , the instantaneous e.m.f. is
1. 10 V
2.
3. 5 V
4. 1 V
If a current I given by flows in an ac circuit across which an ac potential of has been applied, then the power consumption P in the circuit will be
1.
2.
3.
4. P = 0
An alternating current is given by the equation . The r.m.s. current is given by
1.
2.
3.
4.
1. | \( 0.2~\text{sec}\) | 2. | \( 0.25~\text{sec}\) |
3. | \(25 \times10^{-3}~\text{sec}\) | 4. | \(2.5 \times10^{-3}~\text{sec}\) |