Section 1 - Basic Electrical Engineering

Question 1

Ohm's law is valid only for:

A. Non-linear resistors at all temperatures

B. Linear (ohmic) conductors at constant physical conditions

C. Semiconductors at all temperatures

D. Superconductors only

Question 2

The equivalent resistance of two resistors R1 and R2 connected in parallel is:

A. R1 + R2

B. (R1 * R2) / (R1 + R2)

C. R1 - R2

D. (R1 + R2) / (R1 * R2)

Question 3

The RMS value of a purely sinusoidal AC waveform of peak value Vm is:

A. Vm

B. Vm / sqrt(2)

C. 2 Vm / pi

D. Vm / 2

Question 4

The average value of a purely sinusoidal AC waveform over a half cycle is:

A. Vm

B. Vm / sqrt(2)

C. 2 Vm / pi

D. Vm / 2

Question 5

The form factor of a sinusoidal AC waveform is:

A. 1.0

B. 1.11

C. 1.414

D. 0.707

Question 6

The peak (crest) factor of a sinusoidal AC waveform is:

A. 1.0

B. 1.11

C. 1.414

D. 1.732

Question 7

In a purely inductive AC circuit, the current:

A. Leads the voltage by 90 degrees

B. Lags the voltage by 90 degrees

C. Is in phase with the voltage

D. Is 180 degrees out of phase with the voltage

Question 8

In a purely capacitive AC circuit, the current:

A. Leads the voltage by 90 degrees

B. Lags the voltage by 90 degrees

C. Is in phase with the voltage

D. Is 180 degrees out of phase with the voltage

Question 9

The reactance of a capacitor XC = 1 / (omega C) with increasing frequency:

A. Increases

B. Decreases

C. Remains constant

D. Becomes infinite

Question 10

The reactance of an inductor XL = omega L with increasing frequency:

A. Increases

B. Decreases

C. Remains constant

D. Becomes zero

Question 11

In an AC circuit, the power factor is defined as:

A. The ratio of reactive power to apparent power

B. The ratio of real (active) power to apparent power

C. The ratio of RMS voltage to RMS current

D. The ratio of peak power to average power

Question 12

For a purely resistive load, the power factor is:

A. Unity (1)

B. Zero

C. 0.5 lagging

D. 0.707 leading

Question 13

A load with a lagging power factor is predominantly:

A. Capacitive

B. Inductive

C. Purely resistive

D. Superconducting

Question 14

Power factor correction is generally achieved for inductive loads by connecting:

A. An inductor in series

B. A capacitor in parallel (shunt) with the load

C. A resistor in series

D. Another inductive load in parallel

Question 15

The apparent power in an AC circuit is measured in:

A. Watts (W)

B. Volt-amperes (VA)

C. Volt-amperes reactive (VAR)

D. Joules

Question 16

The reactive power in an AC circuit is measured in:

A. Watts (W)

B. Volt-amperes (VA)

C. Volt-amperes reactive (VAR)

D. Kilowatt-hours (kWh)

Question 17

For a balanced 3-phase star (Y) connected system, the relationship between line and phase quantities is:

A. V_L = V_ph, I_L = sqrt(3) I_ph

B. V_L = sqrt(3) V_ph, I_L = I_ph

C. V_L = V_ph, I_L = I_ph

D. V_L = sqrt(3) V_ph, I_L = sqrt(3) I_ph

Question 18

For a balanced 3-phase delta connected system, the relationship between line and phase quantities is:

A. V_L = V_ph, I_L = sqrt(3) I_ph

B. V_L = sqrt(3) V_ph, I_L = I_ph

C. V_L = V_ph, I_L = I_ph

D. V_L = sqrt(3) V_ph, I_L = sqrt(3) I_ph

Question 19

The total power in a balanced 3-phase system is given by:

A. 3 V_ph I_ph cos(phi)

B. sqrt(3) V_L I_L cos(phi)

C. V_L I_L cos(phi)

D. Both (a) and (b) are correct expressions

Question 20

In a balanced 3-phase 4-wire star-connected system feeding a balanced load, the neutral wire current is:

A. Equal to the phase current

B. sqrt(3) times the phase current

C. Zero

D. Equal to the line current

Question 21

The advantage of 3-phase power over single-phase power is:

A. 3-phase machines are smaller and lighter for the same power rating and have smoother torque

B. 3-phase power always requires fewer wires

C. 3-phase generators are cheaper for household use

D. 3-phase power cannot be transmitted over long distances

Question 22

Electric power transmission is done at high voltage mainly to:

A. Increase transmission losses

B. Reduce line current and hence reduce I^2 R losses in the conductors

C. Improve the power factor at the receiving end

D. Reduce the size of generators

Question 23

In a domestic electric supply, MCBs (Miniature Circuit Breakers) are used primarily to protect against:

A. Under-voltage only

B. Overload and short-circuit currents

C. Frequency variation

D. Power factor changes

Question 24

Earthing (grounding) of electrical equipment is done primarily to:

A. Increase the operating efficiency of the equipment

B. Protect users from electric shock and provide a safe path for fault currents

C. Improve the power factor

D. Reduce harmonics in the supply

Question 25

The commercial unit of electrical energy consumption is:

A. Watt

B. Watt-hour

C. Kilowatt-hour (unit / kWh)

D. Joule

Questions

Section 1 - Basic Electrical Engineering - Set 1