The total current delivered to a number of devices connected in parallel is the

Question

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 1750-W toaster, a 1090-W iron, and a 1250-W microwave oven are turned on in a kitchen. As the drawing shows, they are all connected through a 20 A circuit breaker (which has negligible resistance) to an ac voltage of 120 V.

(a) Find the equivalent resistance of the three devices.

Explanation / Answer

here

P = V^2 / R

R = V^2 / P

R1 = 120^2 / 1750 = 8.22 ohm for toaster

then

R2 = 120 * 120 / 1090 = 13.21 ohm for iron

then

R3 = 120^2 / 1250 = 11.52 ohm for microwave

then the equivalent resistance of the circuit is

Req = V^2 / Ptotal

Req = 120 * 120 ( 1750 + 1090 + 1250 )

Req = 3.52 ohm

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.