Basic Electronics Interview Questions and Answers:

1. What is difference between active and passive devices?

Ans. In passive devices, the time average power delivered to the device over an infinite time period is always greater than or equal to zero while active devices are capable of supplying power.

2. Why is it necessary to connect an electrolytic capacitor in a circuit with correct polarity?

Ans. It needs to be strongly emphasized that the electrolytic capacitor should only be connected in a circuit with the proper polarities. If one connects the positive lead of the capacitor to the negative lead of a circuit, chemical action by the electrolyte will rupture the oxide dielectric and destroy the capacitor. (With reversed polarity, the oxide no longer acts like an insulator and as a result, a substantial leakage current can flow and disintegrate the oxide).

3. Write the properties of ideal voltage source.

Ans. An ideal voltage source is a constant voltage source and is capable of supplying any current at a given voltage. The internal resistance of an ideal voltage source is zero and therefore, the terminal voltage (voltage across the load) is always equal to the source emf and is independent of the magnitude of current supplied.

There are two noteworthy points regarding ideal voltage source.
1. Ideal voltage source cannot he short circuited
2. Two ideal voltage sources of unequal output cannot be placed in parallel.

4. Enlist properties of voltage and current sources.
Or
What are the properties of ideal voltage and current sources?

Ans. Voltage and current sources are energy sources such as batteries, dynamos, alternators, photoelectric cells, metadyne generators etc.

The energy source (voltage or current) may be independent or dependent. A source is said to be independent when it does not depend on any other quantity in the circuit. A dependent source is one which depends on some other quantity in the circuit.

Voltage source is said to be an ideal or constant voltage source if it is capable of supplying any current at a given voltage. A voltage source having zero internal resistance is known as an ideal or constant voltage source.
Similarly current source is said to be an ideal or constant current source if it is capable of supplying a constant current to a load even if its impedance varies.

Practically, a voltage source is not different from a current source. In fact, a source can either operate as a current source or as a voltage source. It merely depends upon its operating conditions. If load impedance is very large in comparison to internal impedance of the source, it will be advantageous to treat the source as a voltage source. On the other hand, if the load impedance is very small in comparison to the internal impedance of the source, it is better to represent the source as a current source. From the circuit point of view it does not matter at all whether the source is treated as a voltage source or a current source. In fact, it is possible to convert a voltage source into a current source and vice versa.

5. What are respective values of internal resistances of ideal voltage and ideal current sources? Is it possible to convert an ideal voltage into an ideal current source or vice versa?

Ans. Internal resistances of ideal voltage and ideal current sources are zero and infinite respectively.
It is not possible to convert ideal voltage source into ideal current source and vice versa.

6. What is meant by “potential divider”?

Ans. The voltage divider is a high resistance connected across the supply mains and is used to provide a variable voltage from a constant supply voltage.