The specification on a heater coil is `250 V, 500 W`. Calculate the resistance of the coil. What will be the resistance of a coil of `1000W` to operate at the same voltage?

Answer

A, B

Explanation

(a) The power consumed by a coil of resistance R when connected across a supply V is `
`P(V^2)/(R)`
` The resistance of the heater coil is, therefore `
`R=(V^2)/(P)`
` `
`(250)^2/(500) = ((62500))/(500)`
` = 125Omega (b) If `
`P= 1000W`
` then `
`R=(V^2)/(P)`
`=(62500)/(1000) = 62.5 Omega`