Question

A circuit has a fuse of 5 A. What is the maximum number of 100 W(220 V) bulbs that can be safely used in the circuit?
(class 10 CBSE SAMPLE PAPER 2017-18 SCIENCE)

Answer 1

Solution:
Let ‘x’ bulbs can be used safely.

Given:
Power of 1 bulb = 100 W
Power of x bulbs(P)= 100(x) W
Potential difference (V)= 220 volts
Current (I) = 5 amperes

Power(P)= V× I
100 × x = 220 × 5
x= (220×5)/100
x= 22/2= 11

x= 11
Hence, a number of 11 bulbs can be used.

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Answer 2

Let y' bulbs can be used safely




. Power of 1 bulb 100 W Power of y bulbs



(P)- 100 (y) W Potential difference


(V) 220 volts Current (I) 5 amperes Power (P)- Vx l 100 x y



220 x 5 (220x5)/100 x- 22/2 11








Hence, a number of 11 bulbs can be used