The voltage is 125 v

Question

a) on an LED tv with an overall internal resistance of 24.0 Ω. How much current will the television draw?

b) if they watch for 12.5 hours how much does it cost to power the television if the cost is a flat rate of 10 cents per kWh?

c) After watching TV you go to Europe, you bring your hairdryer, which has a power rating of 1.8 kW based on a Canadian outlet voltage of 120 V nominally. How much power will the hairdryer use if it is plugged into a European wall outlet that supplies 240 V?

Answer 1

a) Voltage V = current I * resistance R, so 125 = 24*I and I = 5.21 Amps.

b) Power P = I*V = (5.21)(125) = 651 Watts = 0.651 kW. For 12.5 hours, total energy = P*t = (0.651)(12.5) = 8.14 kWh. At $0.10 per kWh, then cost is (8.14)(0.10) = $0.81.

c) Another equation for power is P = V² /R. We're given that P = 1.8 kW = 1,800 W. Find R from the Canadian parameters: R = V² /P = (120)² / (1,800 W) = 8.0 Ω of resistance. When we go where V = 240 volts, then power P' = (240)² /(8.0) = 7,200 W = 7.2 kW (4 times more power than in Canada).