If the length of the filament of a heater is reduced by `10%`, the power of the heater will

Options

A. increase by about `9%`
B. increase by about `11%`
C. decrease by about `11%`
D. decrease by about 9%`

Answer

B

Explanation

(b) New resistane: `R' = (rho(0.9L))/(A) = 0.9 R`
`P' = (V^(2))/(R') = (V^(2))/(0.9 R) = (P)/(0.9)`
Increase in power : `(P' - P)/(P) xx 100 = (100)/(9) = 10%`