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

Options

A. increases by about `9%`
B. increases by about `11%`
C. increases by about `19%`
D. decreases by about `10%`

Answer

B

Explanation

`P = (V^(2))/( rho (l)/(a)) or P prop (1)/( l) , P' prop (1)/( l - (10)/(100)l)`
`(P')/(P) = ( 10)/(9) or ((P')/(P) -1) xx 100 = ((10)/(9) - 1) xx 100`
`(P' -P)/(P) xx 100 = (100)/(9) ~~ 11`