An alternating current having peak value 14 A is used to heat a metal wire. To produce the same heating effect, a constant current i can be used where i is

1.  14 A

2.  about 20 A

3.  7 A

4.  about 10 A

A constant current of 2.8 A exists in a resistor. The RMS current is

1.  2.8 A

2.  about 2 A

3.  1.4 A

4.  undefined for a direct current

An inductor, a resistor and a capacitor are joined in series with an AC source. As the frequency of the source is slightly increased from a very low value, the reactance

(a) of the inductor increases
(b) of the resistor increases
(c) of the capacitor increases
(d) of the circuit increases

Choose the correct option 

1. (a) only

2. (b), (c)

3. (c), (d)

4. (a), (d)

The reactance of a circuit connected to an AC circuit is zero. It is possible that the circuit contains 

(a) an inductor and a capacitor
(b) an inductor but no capacitor
(c) a capacitor but no inductor
(d) neither an inductor nor a capacitor

Choose the correct option

1.  (a) only

2. (b), (c)

3. (c), (d)

4. (a), (d)

In an AC series circuit, the instantaneous current is zero when the instantaneous voltage is maximum. Connected to the source may be a 

(a) pure inductor
(b) pure capacitor
(c) pure resistor
(d) combination of an inductor and a capacitor

Choose the correct option 

1. (a), (b), (d)

2. (b), (c), (a)

3. (c), (d), (a)

4. (a), (d), (c)

An inductor-coil having some resistance is connected to an AC source. Which of the following quantities have zero average value over a cycle?

(a) current
(b) induced emf in the inductor
(c) Joule heat
(d) magnetic energy stored in the inductor

Choose the correct option 

1. (a) only

2. (b), (c)

3. (c), (d)

4. (a), (b)

The AC voltage across a resistance can be measured using 

(a) a potentiometer
(b) a hot-wire voltmeter
(c) a moving-coil galvanometer
(d) a moving-magnet galvanometer

Choose the correct option 

1. (a), (b)

2. (b) only

3. (c), (d)

4. (a), (d)

To convert mechanical energy into electrical energy, one can use 

(a) DC dynamo
(b) AC dynamo
(c) motor
(d) transformer

Choose the correct option 

1. (a) only

2. (b), (c) 

3. (a), (b) 

4. (a), (d) 

An AC source rated 100 V (rms) supplies a current of 10 A (rms) to a circuit. The average power delivered by the source 
(a) must be 1000 W.
(b) may be 1000 W.
(c) may be greater than 1000 W.
(d) may be less than 1000 W.
Choose the correct option:
1. (a) only
2. (b), (c)
3. (b), (d)
4. (a), (d)

An alternating current is given by 

i – i₁ cos ωt + i₂ sin ωt

The rms current is given by

1.    \(\frac{i_{1}+i_{2}}{\sqrt{2}}\)

2.  \(\frac{\left|i_{1}+i_{2}\right|}{\sqrt{2}}\)

3.   \(\sqrt{\frac{i_{1}^{2}+i_{2}^{2}}{2}}\)

4.  \(\sqrt{\frac{i_{1}^{2}+i_{2}^{2}}{\sqrt{2}}}\)