When a 14.0-A current flows through an 8.00-Ω device for 24.0 hours,how much does this cost if energy costs $0.0900 per kW ∙ h?
A)$0.24
B)$1.04
C)$2.16
D)$3.39

Question

Quizplus · Accepted Answer

First, calculate the energy used in kilowatt-hours (kWh). The power (P) in watts (W) is given by P = IV, where I is the current in amperes (A) and V is the voltage (V). Since V = IR (Ohm's Law), where R is the resistance in ohms (Ω), we find P = I^2R. For a 14.0-A current through an 8.00-Ω device, P = (14.0)^2 * 8.00 = 1568 W = 1.568 kW. The energy used over 24.0 hours is E = P * time = 1.568 kW * 24.0 h = 37.632 kWh. At $0.0900 per kWh, the cost is 37.632 kWh * $0.0900/kWh = $3.39.

When a 140-A Current Flows Through an 8