Question

An electrician must decide between 3 heaters. The wire that she is using is rated 15A maximum, anything beyond that is a fire hazard. Two of the heaters operate off a standard 120V circuit. One is rated 900W and the other 1800W. The third operates off a 240V circuit and can deliver 3000W of power. Calculate the amount of current for each.

Answer 1

Use the formula: $P=IV$, where P is power (watts), I is current (amperes) and V is potential difference (volts).

For the first heater:
$900W = I_{1}*120V$
$I_{1} = 7.5A$


For the second heater:
$1800W = I_{2}*120V$
$I_{2} = 15A$


For the third heater:
$3000W = I_{3}*240V$
$I_{3} = 12.5A$