1. The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If the frequency is increased to 100 Hz, reactance becomes ?

5 ?

10 ?

16 ?

30 ?

Answer: 10 ?

Explanation:


2. An AC. voltage is impressed across a pure resistance of 3.5 ohms in parallel with a pure inductance of impedance of 3.5 ohms ?

the current through the resistance is more

the current through the resistance is less

both resistance and inductance carry equal currents

none of the above

Answer: both resistance and inductance carry equal currents

Explanation:


3. An R-L-C circuit consists of a resistance of 1000 n, an inductance of 100 mH and a capacitance of 10 ?F. The Q-factor of the circuit is ?

10

20

50

100

Answer: 100

Explanation:


4. Which of the following statement is incorrect ?

Ideal voltage source is one whose internal resistance is zero

Ideal voltage source is one whose internal conductance is zero

Ideal voltage source is one whose generated voltage is equal to, the available terminal voltage

Ideal current source is one whose internal conductance is zero

Answer: Ideal voltage source is one whose internal conductance is zero

Explanation:


5. The dual of a loop is ?

twig

node pair

mesh

tree

Answer: node pair

Explanation:


6. The reflection coefficient of the simplest standing wave is ?

-1

1

zero

infinity

Answer: 1

Explanation:


7. A pure capacitor connected across an A.C. voltage consumed 50 W. This is due to ?

the capacitive reactance in ohms

the current flowing in capacitor

the size of the capacitor being quite big

the statement is incorrect

Answer: the statement is incorrect

Explanation:


8. Two wattmeters connected to measure the power input to a balanced 3-? circuit indicate 2500 W and 500 W respectively. What is the power factor ?

0.355

0.455

0.555

0.655

Answer: 0.655

Explanation:


9. In R-L-C series resonant circuit magnitude of resonance frequency can be changed by changing the value of ?

R only

L only

C only

L or C

Answer: L or C

Explanation:


10. The r.m.s. value of alternating current is given by steady (D.C.) current which when flowing through a given circuit for a given time produces ?

the more heat than produced by A.C. when flowing through the same circuit

the same heat as produced by A.C. when flowing through the same circuit

the less heat than produced by A.C. flowing through the same circuit

none of the above

Answer: the same heat as produced by A.C. when flowing through the same circuit

Explanation: