An inductor of \(20~\text{mH}\), a capacitor of \(100~\mu \text{F}\), and a resistor of \(50~\Omega\) are connected in series across a source of emf, \(V=10 \sin (314 t)\). What is the power loss in this circuit?
1. \( 0.79 ~\text{W} \)
2. \( 0.43 ~\text{W} \)
3. \( 2.74 ~\text{W} \)
4. \( 1.13 ~\text{W}\)
A 50 Hz a.c. source of 20 volts is connected across R and C as shown in the figure below.
If the voltage across R is 12 volts, then the voltage across C will be:
1. | 8 V |
2. | 16 V |
3. | 10 V |
4. | not possible to determine unless values of R and C are given |
What is the value of inductance L for which the current is a maximum in a series LCR circuit with C=10 μF and = 1000 s-1?
1. | 10 mH |
2. | 100 mH |
3. | 1 mH |
4. | Cannot be calculated unless R is known |
Alternating current cannot be measured by a D.C. ammeter because:
1. | A.C. cannot pass through D.C. Ammeter |
2. | A. C. changes direction |
3. | Average value of current for the complete cycle is zero |
4. | D.C. Ammeter will get damaged |
For a LCR series circuit with an A.C. source of angular frequency
1. | circuit will be capacitive if \(\omega>\frac{1}{\sqrt{LC}} \) |
2. | circuit will be inductive if \(\omega=\frac{1}{\sqrt{LC}} \) |
3. | power factor of circuit will be unity if capacitive reactance equals inductive reactance |
4. | current will be leading voltage if \(\omega>\frac{1}{\sqrt{LC}} \) |
In an L-R circuit, the inductive reactance is equal to the resistance R of the circuit. An emf of E = E0cos(ωt) is applied to the circuit. The power consumed by the circuit is:
1.
2.
3.
4.
A series AC circuit has a resistance of 4 and an inductor of reactance 3 . The impedance of the circuit is z1. Now when a capacitor of reactance 6 is connected in series with the above combination, the impedance becomes will be:
1. 1 : 1
2. 5 : 4
3. 4 : 5
4. 2 : 1
An inductor (L) and resistance (R) are connected in series with an AC source. The phase difference between voltage (V) and current (i) is . If the phase difference between V and i remains the same, then the capacitive reactance and impedance of the L-C-R circuit will be:
1. 2R, R
2. R, R
3. R, R
4. 2R, R
An \(AC\) voltage is applied to a resistance \(R\) and an inductor \(L\) in series. If \(R\) and the inductive reactance are both equal to \(3~ \Omega, \) then the phase difference between the applied voltage and the current in the circuit will be:
1. | \( \pi / 4\) | 2. | \( \pi / 2\) |
3. | zero | 4. | \( \pi / 6\) |
A coil of self-inductance L is connected in series with a bulb B and an AC source. The brightness of the bulb decreases when:
1. | Frequency of the AC source is decreased |
2. | The number of turns in the coil is reduced |
3. | A capacitance of reactance Xc=XL is included in the same circuit |
4. | An iron rod is inserted in the coil |