# Network Theory Questions and Answers – Voltage and Current Sources

This set of Network Theory Multiple Choice Questions & Answers (MCQs) focuses on “Voltage and Current Sources”.

1. Pick the incorrect statement among the following.
a) Inductor is a passive element
b) Current source is an active element
c) Resistor is a passive element
d) Voltage source is a passive element

Explanation: Energy sources(voltage or current sources) are active elements, capable of delivering power to some external device.

2. For a voltage source to be neglected, the terminals across the source should be ___________
a) replaced by inductor
b) short circuited
c) replaced by some resistance
d) open circuited

Explanation: If the voltage source is to be neglected, it can be replaced simply by means of a wire i.e, it should be short circuited.

3. Voltage source and terminal voltage can be related as ___________
a) terminal voltage is higher than the source emf
b) terminal voltage is equal to the source emf
c) terminal voltage is always lower than source emf
d) terminal voltage cannot exceed source emf

Explanation: A practical voltage source can be represented with a resistance in series with the source. Hence, there would be some voltage drop at the resistor and the terminal voltage is always lower than the source emf.

4. In case of ideal current sources, they have ___________
a) zero internal resistance
b) low value of voltage
c) large value of currrent
d) infinite internal resistance

Explanation: For the ideal current sources, the current is completely independent of voltage and it has infinte internal resistance.

5. In a network consisting of linear resistors and ideal voltage source, if the value of resistors are doubled, then voltage across each resistor ___________
a) increases four times
b) remains unchanged
c) doubled
d) halved

Explanation: Even on changing the values of linear resistors, the voltage remains constant in case of ideal voltage source.
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6. A practical current source can also be represented as ___________
a) a resistance in parallel with an ideal voltage source
b) a resistance in parallel with an ideal current source
c) a resistance in series with an ideal current source
d) none of the mentioned

Explanation: A practical current source could be represented with a resistor in parallel with an ideal current source.

7. A practical voltage source can also be represented as ___________
a) a resistance in series with an ideal current source
b) a resistance in series with an ideal voltage source
c) a resistance in parallel with an ideal voltage source
d) none of the mentioned

Explanation: A practical voltage source could be represented with a resistor in series with an ideal voltage source.

8. Constant voltage source is ___________
a) active and bilateral
b) passive and bilateral
c) active and unilateral
d) passive and unilateral

Explanation: Voltage source is an active element and is unilateral.

9. Which of the following is true about an ideal voltage source?
a) zero resistance
b) small emf
c) large emf
d) infinite resistance

Explanation: An ideal voltage source with zero internal resistance.

10. A dependent source ___________
a) may be a current source or a voltage source
b) is always a voltage source
c) is always a current source
d) none of the mentioned

Explanation: Dependent sources can either be current sources or voltage sources.

11. With some initial change at t = 0+, a capacitor will act as ___________
a) open circuit
b) short circuit
c) a current source
d) a voltage source

Explanation: At t=0+, the capacitor starts charging to a particular voltage and acts as a voltage source.

12. If a current source is to be neglected, the terminals across the source are ___________
a) replaced by a source resistance
b) open circuited
c) replaced by a capacitor
d) short circuited

Explanation: As the ideal current source has infinite resistance, it can be neglected by open circuiting the terminals.

13. A constant current source supplies a electric current of 200 mA to a load of 2kΩ. When the load changed to 100Ω, the load current will be ___________
a) 9mA
b) 4A
c) 700mA
d) 12A

Explanation: From Ohm’s law, resistance is inversely proportional to the current.

14. A voltage source having an open circuit voltage of 200 V and internal resistance of 50Ω is equivalent to a current source of ___________
a) 4A with 50Ω in parallel
b) 4A with 50Ω in series
c) 0.5A with 50Ω in parallel
d) none of the mentioned

Explanation: A voltage source with resistance in series can be replaced with a current source with the resistance in parallel.

15. A voltage source of 300 V has internal resistance of 4Ω and supplies a load having the same resistance. The power absorbed by the load is?
a) 1150 W
b) 1250 W
c) 5625 W
d) 5000 W

Explanation: Power absorbed = I2R.

Sanfoundry Global Education & Learning Series – Network Theory.

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