AC BASICS AND NETWORKS

1. The rms value of a sine wave is 100 A. Its peak value is
a) 70.7 A
b) 141 A
c) 150 A
d) 282.8 A
ans: 2

2. The rms value of the resultant current in a wire which carries a dc current of 10 A and a sinusoidal alternating current of peak value 20 A is
a) 14.1 A
b) 17.3 A
c) 22.4 A
d) none of the above
ans: b

3. A boiler at home is switched on to the AC mains supplying power at 230 V, 50 Hz. The frequency of instantaneous power consumed is
a) 0 Hz
b) 50 Hz
c) 100 Hz
d) 150 Hz
ans: c

4. Unit of inductive reactance is
a) Henry
b) millihenry
c) Wb
d) Ohm
ans: d

5. A 10 mH inductor carries a sinusoidal current of 1A  rms at a frequency of 50 Hz. The average power dissipated by the indicator is
a) 0 W
b) 0.25 W
c) 0.5 W
d) 1.0 W
ans: a

6. A circuit component that opposes the change in circuit voltage is
a) resistance
b) capacitance
c) inductance
d) all of the above
ans: b

7. The reactance offered by a capacitor to AC of frequency 50 Hz is 10 ohm. If the frequency is increased to 100 Hz , reactance becomes
a) 20 ohm
b) 5 ohm
c) 2.5 ohm
d) 30 ohm
ans: b

8. The pf of a practical inductor is
a) unity
b) zero
c) lagging
d) leading
ans: c

9. The power factor of an ordinary electric bulb is
a) zero
b) unity
c) slightly more than unity
d) slightly less than unity
ans: d

10. A 2-terminal network consists of one of the RLC elements. The element is connected to ans ac supply. The current through the element is I A. When an inductor is inserted in series between the source and the element , the current through the element becomes 2I A . What is the element?
a) A resistor
b) An inductor
c) A capacitor
d) cannot be a single element
ans: c