The total current delivered to a number of devices connected in parallel is the sum of the individual currents in each device. Circuit breakers are resettable automatic switches that protect against a dangerously large total current by "opening" to stop the current at a specified safe value. A 1500 W toaster, a 1030 W iron, and a 1000 W microwave oven are turned on in a kitchen. As the drawing shows, they are all connected through a 20 A circuit breaker to an ac voltage of 120 V.Find the equivalent resistance of the three devices and the total current delivered by the source. Answer in ohms and amps.
Power P = V*I = V^2/R
resistance R = V^2/P = 120^2/1500 = 9.60 ohm --Answer
current I = P/V = 1500/120 = 12.5 ...
The solution provides a clear and concise worked method to obtaining the resistances of a microwave, iron and toaster connected in parallel with circuit breakers and ac current.