# Basic Electrical Engineering MCQs Part 11

Basic Electrical Engineering MCQs Part 11

## Two identical heater coils are connected in parallel across mains. If one of coil breaks the other

Two identical heater coils are connected in parallel across mains. If one of coil breaks the other:

1. Develops lower temperature
2. Develops higher temperature
3. Develops same temperature as before
4. None of these

Correct answer: 3. Develops same temperature as before

## What maximum voltage can be provided across a 1 W, 225 Ω resistor without exceeding rated power dissipation

What maximum voltage can be provided across a 1 W, 225 Ω resistor without exceeding rated power dissipation:

1. 5 W
2. 10 W
3. 15 W
4. 20 W

Solution:

V = √P * R = √(1 * 225) = 15 W

## Two electric lamps of 40 W, 220 V each are connected in series across 220 V source. The power consumed by the combination of two lamps is:

Two electric lamps of 40 W, 220 V each are connected in series across 220 V source. The power consumed by the combination of two lamps is:

1. 10 W
2. 20 W
3. 40 W
4. 80 W

Explanation:

PT = (P1 * P2)/(P1 + P2) = 20 W

## Lamps used for lighting homes are connected in

Lamps used for lighting homes are connected in:

1. Series configuration
2. Parallel configuration
3. Series-parallel configuration
4. None of above

## Two lamps of 80 W and 200 W rated for 220 V are connected in series and a 440 volts are applied across them. Which lamp will fuse

Two lamps of 80 W and 200 W rated for 220 V are connected in series and a 440 volts are applied across them. Which lamp will fuse:

1. 80 W
2. 200 W
3. Both will fuse
4. Both will work fine

Resistance of 80 Watt lamp for rated voltage = V²/P1 = 220²/80 = 605 Ω

Resistance of 200 Watt lamp for rated voltage = V²/P1 = 220²/200 = 242 Ω

———————

Total circuit resistance (Rt) = R1 + R2 = 605 Ω + 242 Ω= 847 Ω

———————

Circuit current (I) = 440 V/847 Ω = 0.519A

———————

Voltage across 80 W lamp = IR1 = 0.519 * 605 Ω = 314 V

Voltage across 200 W lamp = IR1 =  * 242 Ω = 126 V

———————

Since voltage across 80 W lamp is more than rated voltage, the 80 W lamp will fuse.