Electricity Question?

Question

Ok, i need a little help with this. It's involving electricity, obvioiusly. So, an object has a resistance of 15 ohms, a voltage of 45 volts, an electric current of 3, the power of it is 135. After giving you these facts, I'd appreciate it if you could answer the question. The question is

What is the cost of operating this object for 10 hours at a rate of $0.08 per kWh?

I didn't understand the question, so maybe someone that understands electricity better than me can help solve this question. If you have taken the time to even read my question, thank you. Any help is highly appreciated.

Answer 1

You calculated your power correctly. 135 Watts is also 0.135 kWatt.

10 hours * 0.135 kW = 1.35 kWhr

1.35 kWhr * $0.08 / kWhr = (you can finish the math).

.

Answer 2

A lot of that information isn't needed (even though it is accurate).
A watt is a unit of power consumption (or generation) equal to 1 Joule per second of energy. Saying that the circuit consumes 135 watts means that it's turning 135 Joules of energy into heat every second.
Now, that means that 135 J every second will come up to
135 J/s* 3,600 s/hr * 10 hrs = 4,860,000 Joules total used.
Power is sold in kwh because you pay for the energy used, -not- the rate at which you use it. One kwh is 1,000 J/s * 3600 s/hr = 3,600,000 J of energy used. So the energy consumed by the circuit over a 10 hour period would be 4,860,000/3,600,000 which is 1.35 kwh which would cost 1.35 * .08 = 10.8 cents.

Doug

Answer 3

P=IV, 45V x 3 amps = 135 Watts

total kW-hr is 135 Watts for 10 hours, is 1350 W-hrs or 1.35 kW-hrs

1.35 kW-hr * 0.08 $/kW-hr = $0.108 ≈ 11 cents