If the length of a heater coil is reduced by 10% of its original length, then Power consumed by heater will?

Power (P) = I^2R

I = Current, R = Resistance

R = rho*l/A

rho = Resistivity, l = Length, A = Cross sectional Area

Now l1= 0.9l

R1 = rho*l1/A = rho*0.9l/A = 0.9R

New Power (P1) = I^2R1 = I^2*0.9R = 0.9P

Hence the Power will also reduce by 10%.