Question

A motor that pumps up water to a tank requires 10kW power. Its operating voltage is 220V. The only available resistor has a resistance of 11Ω. We know that we must use n such resistors in series and p such series resistor combinations in parallel. The values of n and p are respectively

Answer 1

Equation of power,
P = V^2/R
R = V^2/P
R = 220^2 / 10000
R = 4.84 Ω

So effective resistance will be 4.84 Ω

n resistors in series that is n×11 = 11n Ω

This 11n Ω in parallel means ie n11/p, and it equal total resistance 4.84Ω.

ie;
4.84 = n11/p
p/n = 1100/484
p/n = 25/11

p = 25
n = 11
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