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. increase by about `19%`
D. decrease by about `10%`

Answer

B

Explanation

`P=V^2/R` or `P prop 1/R`
`P_2/P_1=R_1/R_1=l_1/l_2` (as R `prop` 1)
`:. P_(2) = ((l_(1))/(l_(2))) P_(1) = ((l)/(0.9 l)) P_(1) = 1.11 P_(1)`
so, power will increase by `11%`