Homework Help: Physics -Electricity

Posted by Anonymous on Monday, February 6, 2012 at 11:37am.

Several appliances are supplied with a potential difference of 314 V and are operated continuously for a 24 h period. How much energy is used if the appliance is a 30.0 W stereo?
Answer in units of J

How much of energy is used if the appliance is an electric oven that draws 70.0 A of current?
Answer in units of J

How much energy is used if the appliance is a television with a resistance of 10.0 ?
Answer in units of J

Any help or information on how to solve these would be greatly appreciated, Thanks!

Physics -Electricity - Damon, Monday, February 6, 2012 at 11:49am
well, first figure out the number of seconds
24 h * 60 min/h * 60 s/min = 8.64 *10^4 s

a Watt is a Joule/second so Joules = Watts * seconds

30 *8.64 * 10^4 = 2.59*1^6 Joules

watts = Volt * amps
watts = 314 * 70
Joules = 314*70 * 8.64*10^4

watts = V^2/r = (314)^2/10 ohms
Joules = (314^2/10) *6.64*10^4

314 is a VERY strange voltage for appliances.
Physics -Electricity - Anonymous, Monday, February 6, 2012 at 11:56am
Life saver, thanks!

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