# Basic Electrical Engineering MCQs Part 15

Basic Electrical Engineering MCQs Part 15

## Two electric bulbs having resistances in ratio 1:2 are connected in parallel to a constant voltage source. The power dissipated by the bulbs are in ratio

Two electric bulbs having resistances in ratio 1:2 are connected in parallel to a constant voltage source. The power dissipated by the bulbs are in ratio:

1. 1:1
2. 1:2
3. 2:1
4. None of these

## Of two bulbs in a house, one glows brighter than the other, which of the two has larger resistance

Of two bulbs in a house, one glows brighter than the other, which of the two has larger resistance:

1. The bright bulb
2. The dim bulb
3. Both have same resistance
4. Brightness is independent of resistance

Correct answer: 2. The dim bulb

## A 1000 W heater is designed to operate of 230 V line. If line voltage drops to 200 V, the percentage drop is heat output is

A 1000 W heater is designed to operate of 230 V line. If line voltage drops to 200 V, the percentage drop is heat output is:

1. 24.39%
2. 34.92%
3. 54.88%
4. 65.68%

Solution:

P = 230²/R

P’ = 200²/R

————–

P’/P = (200/230)²

————–

%age drop in heat output = (1 – P’/P) * 100

[1 – (200/230)² ]* 100 = 24.39%

## Two electric bulbs have tungsten filament of same length. If one of them gives 50 W and other one 100 W, then which of following is correct:

Two electric bulbs have tungsten filament of same length. If one of them gives 50 W and other one 100 W, then which of following is correct:

1. 50 W has thicker filament
2. 100 W has thicker filament
3. Both have filaments of same thickness
4. Insufficient information

Correct answer: 2. 100 W has thicker filament

Solution:

From formula:

R = ρl/a

## The filament of bulb having low resistance is thicked. Sice l is constant in both cases. The 100 W bulb has less resistance as compared to 50 W.  Hence, 100 W has thicker filament

The filament of bulb having low resistance is thicked. Sice l is constant in both cases. The 100 W bulb has less resistance as compared to 50 W.  Hence, 100 W has thicker filament.

Two electrical appliances are connected in parallel to constant voltage supply. If current in one appliance is less than second appliance by 1%, then power of first appliance will be less by what percentage:

1. 1%
2. 2%
3. 3%
4. 99%