Q.

A heater is designed to operate with a power of 1000 W in a 100 V line. It is connected in combination with a resistance of 10 Ω and a resistance R, to a 100 V mains as shown in figure. For the heater to operate at 62.5 W, the value of R should be _____ Ω.               [2024]


Ans.

(5)

Rheater=V2P=(100)21000=10Ω

For heater P=V2RV=PR

V=62.5×10=25 V

i1=7510=7.5 A,  iH=2510=2.5 A

iR=i1-iH=7.5-2.5=5 A

V=IRR=255=5Ω