The variation of EMF with time for four types of generators is shown in the figures. Which amongst them can be called AC voltage?
(a) | (b) |
(c) | (d) |
1. | (a) and (d) |
2. | (a), (b), (c), and (d) |
3. | (a) and (b) |
4. | only (a) |
A circuit when connected to an AC source of \(12~\text{V}\) gives a current of \(0.2~\text{A}\). The same circuit when connected to a DC source of \(12~\text{V}\), gives a current of \(0.4~\text{A}\). The circuit is:
1. | series \({LR}\) | 2. | series \({RC}\) |
3. | series \({LC}\) | 4. | series \({LCR}\) |
A coil of inductive reactance \(31~\Omega\) has a resistance of
\(8~\Omega\). It is placed in series with a condenser of capacitive reactance \(25~\Omega\). The combination is connected to an a.c. source of
\(110~\text{V}\). The power factor of the circuit is:
1. \(0.56\)
2. \(0.64\)
3. \(0.80\)
4. \(0.33\)
The core of a transformer is laminated so that:
1. | energy losses due to eddy currents may be minimized |
2. | the weight of the transformer may be reduced |
3. | rusting of the core may be prevented |
4. | the ratio of voltage in primary and secondary may be increased |
A transformer is used to light a \(100~\text{W}\) and \(110~\text{V}\) lamp from a \(220~\text{V}\) main. If the main current is \(0.5~\text{A}\), the efficiency of the transformer is approximately:
1. \(30\%\)
2. \(50\%\)
3. \(90\%\)
4. \(10\%\)
What is the value of inductance L for which the current is maximum in a series LCR circuit with C = 10 μF and ω=1000 s-1?
1. 100 mH
2. 1 mH
3. cannot be calculated unless R is known
4. 10 mH
In an AC circuit, the emf (e) and the current (I) at any instant are given respectively by
e = E0sint
I = I0sin
The average power in the circuit over one cycle of AC is:
1.
2.
3.
4.
The power dissipated in an L-C-R series circuit connected to an AC source of emf E is:
A \(220\) V input is supplied to a transformer. The output circuit draws a current of \(2.0\) A at \(440\) V. If the efficiency of the transformer is \(80\)%, the current drawn by the primary windings of the transformer is:
1. \(3.6\) A
2. \(2.8\) A
3. \(2.5\) A
4. \(5.0\) A
In the given circuit, the reading of voltmeter V1 and V2 are 300 V each. The reading of the voltmeter V3 and ammeter A are respectively:
1. 150 V, 2.2 A
2. 220 V, 2.2 A
3. 220 V, 2.0 A
4. 100 V, 2.0 A