### 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 e

_{1}= A sin ωt and e_{2}= B sin (ωt − q), then
(a) e

_{1}lags e_{2}by θ
(b) e

_{2}lags e_{1}by θ
(c) e

_{2}leads e_{1}by θ
(d) e

_{1}is in phase with e_{2}
3. From the two voltage equations e

_{A}= E_{m}sin 100πt and e_{B}= E_{m}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 : i

_{1}= 10 sin (ωt + π/3) and i_{2}= 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

**Answers**

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

Two sinusoidal currents are given by the equations : i1 = 100 sin (ωt + π/3) and i2 = 150

ReplyDeletesin (ωt − π/4). The phase difference between them is — degrees full ans