**1. A sine wave has a frequency of 50 Hz. Its angular frequency is _______ radian/second.**

(a) 100 n

(b) 50 jt

(c) 25 jt

(d) 5 n

**Ans: a**

**2. The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If frequency is increased to 100 Hz, reactance becomes_____ohms.**

(a) 2.5

(b) 5

(c) 10

(d) 15

**Ans: c**

**3. The period of a wave is**

(a) the same as frequency

(6) time required to complete one cycle

(c) expressed in amperes

(d) none of the above

**Ans: b**

**4. The form factor is the ratio of**

(a) peak value to r.m.s. value

(6) r.m.s. value to average value

(c) average value to r.m.s. value

(d) none of the above

**Ans: b**

**5. The period of a sine wave is _____ seconds. Its frequency is**

(a) 20 Hz

(b) 30 Hz

(c) 40 Hz

(d) 50 Hz

**Ans: d**

**6. A heater is rated as 230 V, 10 kW, A.C. The value 230 V refers to**

(a) average voltage

(b) r.m.s. voltage

(c) peak voltage

(d) none of the above

**Ans: b**

**7. If two sinusoids of the same frequency but of different amplitudes and phase angles are subtracted, the resultant is**

(a) a sinusoid of the same frequency

(b) a sinusoid of half the original frequency

(c) a sinusoid of double the frequency

(d) not a sinusoid

**Ans: a**

**8. The peak value of a sine wave is 200 V. Its average value is**

(a) 127.4 V

(b) 141.4 V

(c) 282.8 V

(d)200V

**Ans: a**

**9. If two sine waves of the same frequency have a phase difference of JT radians, then**

(a) both will reach their minimum values at the same instant

(b) both will reach their maximum values at the same instant

(c) when one wave reaches its maximum value, the other will reach its minimum value

(d) none of the above

**Ans: c**

**10. The voltage of domestic supply is 220V. This figure represents**

(a) mean value

(b) r.m.s. value

(c) peak value

(d) average value

**Ans: a**

**11. Two waves of the same frequency have opposite phase when the phase angle between them is**

(a) 360°

(b) 180°

(c) 90°

(d) 0°

**Ans: b**

**12. The power consumed in a circuit element will be least when the phase difference between the current and voltage is**

(a) 180″

(b) 90°

(c) 60°

(d) 0°

**Ans: b**

**13. The r.m.s. value and mean value is the same in the case of**

(a) triangular wave

(6) sine wave

(c) square wave

(d) half wave rectified sine wave

**Ans: c**

**14. For the same peak value which of the following wave will ‘have the highest r.m.s. value ?**

(a) square wave

(b) half wave rectified sine wave

(c) triangular wave

(d) sine wave

**Ans: a**

**15. For the same peak value, which of the following wave has the least mean value ?**

(a) half wave rectified sine wave

(b) triangular wave

(c) sine wave

(d) square wave

**Ans: a**

**16. For a sine wave with peak value Imax the r.m.s. value is**

(a) 0.5 Imax

(b) 0.707

(c) 0.9

(d) 1.414 Lmax

**Ans: b**

**17. Form Factor is the ratio of**

(a) average value/r.m.s. value

(b) average value/peak value

(e) r.m.s. value/average value

(d) r.m.s. value/peak value

**Ans: c**

**18. Form factor for a sine wave is**

(a) 1.414

(b) 0.707

(c) 1.11

(d) 0.637

**Ans: c**

**19. For a sine wave with peak value Emax______8.30. the average value is**

(a) 0.636 Emax

(b) 0.707 Emax

(c) 0.434 EWc

(d) lAUEmax

**Ans: a**

**20. For a frequency of 200 Hz, the time period will be**

(a) 0.05 s

(b) 0.005 s

(c) 0.0005 s

(d) 0.5 s

**Ans: b**

**21. The phase difference between voltage and current wave through a circuit element is given as 30°. The essential condition is that**

(a) both waves must have same frequency

(b) both waves must have identical peak values

(c) both waves must have zero value at the same time

(d) none of the above

**Ans: a**

**22. The r.m.s. value of a sinusoidal A.C. current is equal to its value at an angle of______degrees.**

(a) 90

(b) 60

(c) 45

(d) 30

**Ans: c**

**23. Capacitive reactance is more when**

(a) capacitance is less and frequency of supply is less

(b) capacitance is less and frequency of supply is more

(c) capacitance is more and frequency of supply is less

(d) capacitance is more and frequency of supply is more

**Ans: a**

**24. In a series resonant circuit, the impedance of the circuit is**

(a) minimum

(b) maximum

(c) zero

(d) none of the above

**Ans: a**

**25. Power factor of an electrical circuit is equal to**

(a) R/Z

(b) cosine of phase angle difference between current and voltage

(c) kW/kVA

(d) ratio of useful current to total current Iw/I

(e) all above

**Ans: e**