### Basic Electrical Science (A.C. Fundamentals)

1. An a.c. current given by i = 14.14 sin (ωt + π/6) has an r.m.s value of — amperes.
(a) 10
(b) 14.14
(c) 1.96
(d) 7.07
and a phase of — degrees.
(e) 180
(f) 30
(g) − 30
(h) 210

2. If e1 = A sin ωt and e2 = B sin (ωt − q), then
(a) e1 lags e2 by θ
(b) e2 lags e1 by θ
(c) e2 leads e1 by θ
(d) e1 is in phase with e2

3. From the two voltage equations eA = Emsin 100πt and eB = Em sin (100πt + π/6), it is obvious that
(a) A leads B by 30°
(b) B achieves its maximum value 1/600 second before A does.
(c) B lags behind A
(d) A achieves its zero value 1/600 second before B.

4. The r.m.s. value of a half-wave rectified current is 10A, its value for full-wave rectification would be — amperes.
(a) 20
(b) 14.14
(c) 20/π
(d) 40/π

5. A resultant current is made of two components : a 10 A d.c. component and a sinusoidal
component of maximum value 14.14A. The average value of the resultant current is — amperes.
(a) 0
(b) 24.14
(c) 10
(d) 4.14
and r.m.s. value is — amperes.
(e) 10
(f) 14.14
(g) 24.14
(h) 100

6. The r.m.s. value of sinusoidal a.c. current is equal to its value at an angle of — degree
(a) 60
(b) 45
(c) 30
(d) 90

7. Two sinusoidal currents are given by the equations : i1 = 10 sin (ωt + π/3) and i2 = 15
sin (ωt − π/4). The phase difference between them is — degrees.
(a) 105
(b) 75
(c) 15
(d) 60

8. As sine wave has a frequency of 50 Hz. Its angular frequency is — radian/second.
(a) 50/π
(b) 50/2 π
(c) 50 π
(d) 100 π

9. An a.c. current is given by i = 100 sin 100. It will achieve a value of 50 A after — second.
(a) 1/600
(b) 1/300
(c) 1/1800
(d) 1/900

10. The reactance offered by a capacitor to alternating current of frequency 50 Hz is 10Ω.
If frequency is increased to 100 Hz reactance becomes—ohm.
(a) 20
(b) 5
(c) 2.5
(d) 40

12. The current through a resistor has a waveform as shown in Fig. 11.67. The reading
shown by a moving coil ammeter will be— ampere.
(a) 5/ 2
(b) 2.5/ 2
(c) 5/π
(d) 5

1. a, f   2. b      3. b      4. b      5. c, f               6. b      7. a      8. d      9. a      10. b    11. c