Need help with a simple physics question (electricity) (1 Viewer)

[Supaweak]

Hi there just need a bit of help with this question not sure if ive answered it correctly.
Here it is:

A 120 ohm heating element was connected to a 240 volt power supply for 15 minutes. Determine the power dissipated by the heating element



answer i got was 57120 watts...im not sure if i've done it right lol

thanks!

 

[kaz1]

P=V²/R
P=240²/120
P=480 W

I don't think the time affects the power as power is the rate of change of energy.

 

[rama_v]

Power = dW/dt (where W is work), in general.

In this case:
P= d/dt(IVt) = IV = (V/R)*V=V²/R

Power is measured in Watts, which is the same as Joules/s.

 

[Uncle]

Also,
Since W = qV & I = Q/t



P = VI