Question

Two bulbs A and B have the following ratings: A) 40 W, 220 V and B) 20 W, 110 V . The ratio of their resistance is what?

Answer 1

HEY THERE,

Answer:

We know, P = $V^{2}$/R

For bulb (a), P = 40 W, V = 220 W

So, resistance, R = $V^{2}$/P = 2202/40 = 1210 Ω

For bulb (b), P = 40 W, V = 110 W

So, resistance, R = $V^{2}$/P = 1102/40 = 302.5 Ω

Thus, filament of bulb (a) has higher resistance.

The ratio of their resistance is:- Bulb (a) : Bulb (b) = 1210 : 302.5 = 4 : 1

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