Basic Electrical Engineering Questions

Interview Q&A/ Technical Round:

Short Q&A Section:

Q1. What is Electrical Resistance?

Resistance is the property of a material that opposes the flow of electric current. It depends on the material, length, cross-sectional area, and temperature of the conductor. Its unit is ohm (Ω).

Q2. State Ohm’s Law.

Ohm’s Law states that the current flowing through a conductor is directly proportional to the applied voltage, provided temperature remains constant. Mathematically, V = IR.

Q3. What is Electric Current?

Electric current is the rate of flow of electric charge in a conductor. It is measured in amperes (A) and is denoted by I.

Q4. Define Electrical Power.

Electrical power is the rate at which electrical energy is consumed or converted into another form. It is measured in watts (W) and given by P = VI.

Q5. What is Electrical Energy?

Electrical energy is the total work done by an electrical source over time. It is measured in 

watt-hour (Wh) or kilowatt-hour (kWh).

Q6. What is the difference between RMS value and Average value of AC?

The RMS (Root Mean Square) value represents the effective DC equivalent of an AC quantity that produces the same heating effect. The average value is the mean of instantaneous values over a half cycle, mainly used for rectifier analysis and not for power calculations.

Q7. Why is Power Factor important in industrial plants?

A low power factor increases current drawn, leading to higher losses and voltage drops. Improving power factor reduces electricity bills, improves system efficiency, and allows better utilization of transformers and cables.

MCQ Section:

Q1. The SI unit of resistance is:

A) Ampere

B) Volt

C) Ohm

D) Watt

Correct Answer: C

Justification: Resistance is measured in ohms as defined by Ohm’s Law.

Q2. Ohm’s Law is applicable when:

A) Temperature varies

B) Current is alternating

C) Temperature is constant

D) Resistance is zero

Correct Answer: C

Justification: Ohm’s Law assumes constant physical conditions, especially temperature.

Q3. Power consumed in an electrical circuit is given by:

A) V/I

B) I/R

C) VI

D) R/I

Correct Answer: C

Justification: Electrical power is the product of voltage and current.

Q4. In a series circuit, the current is:

A) Different in each resistor

B) Zero

C) Same through all components

D) Maximum at the source only

Correct Answer: C

Justification: In series circuits, the same current flows through all elements.

Q5. Kirchhoff’s Current Law is based on conservation of:

A) Energy

B) Power

C) Voltage

D) Charge

Correct Answer: D

Justification: KCL states that charge entering a node equals charge leaving it.

Q6. In a purely inductive circuit, the phase difference between voltage and current is:

A) 0°

B) 90° lagging

C) 90° leading

D) 180°

Correct Answer: B

Justification: In an inductive circuit, current lags voltage by 90° due to energy storage in the magnetic field.

Q7. Which component causes current to lead voltage?

A) Resistor
B) Inductor
C) Capacitor
D) Transformer

Correct Answer: C

Justification: In a capacitive circuit, current leads voltage due to electric field energy storage.

Q8. Reactance is measured in:

A) Siemens
B) Henry
C) Ohms
D) Farad

Correct Answer: C

Justification: Reactance opposes AC current and is a component of impedance, measured in ohms.

Formulas: