Thermal energy produced in a circuit.?

Question

A 21.2 ohm resistor is connected to a 11.8 V battery. What is the current in the circuit? How much thermal energy is produced in 21.9 min? Answer in units of J.

I figured out the first part of the question using I = V/R. So, for the next part, I have a value for resistance, voltage potential, and current. I'm also given a time. Unfortunately, I have no idea where to move from here. I assume the thermal energy has something to do with electric power, but I can't really grasp how time is a factor. Any help would be appreciated.

Answer 1

The power in watts is I x V. Then apply the time and you have energy

Answer 2

Heh. The rate that thermal energy is produced by a circuit IS THE POWER, silly. Also remember that power is in units of Watts, and that Watts are Joules per second. The power is the number of joules given off per second, which is why you need to know that it's over a certain period of time. Power's given by:

P = V^2 / R

So that means for us:

P = (11.8)^2 / 21.2    J/s
= 6.57 W

Over 21.9 minutes that's:

E = 6.57 J/s * 21.9 min * 60 s/min = 8.63 KJ

8.63 KiloJoules.

[EDIT]
Oops, I multiplied when I should have divided.
[/EDIT]

Answer 3

Silly Garrett … messed up the math.

P = V^2/R = 11.8^2/21.2 Watts = 6.57 W

Run that for 21.9 minutes and you've used
6.57*21.9 Watt*minutes of energy.

The conversion factor needed here to convert from one energy unit to another:
1 kWatt*hr = 3.6*10^6 Joules

Looks like it would be convenient to have those Watt*minutes in kWatt*hrs.
6.57*21.9 Watt*minutes *(1 kWatt/1000 Watts)*(1 hr/60 min) = .00240 kWatt*hrs

Now to convert to Joules:
.00240 kWatt*hrs*(3.6*10^6 Joules/1 kWatt*hr) = 8630 Joules

Answer 4

2 section answer: no longer something is one hundred pc effectual. Inefficiencies generate warmth and it takes a on an analogous time as for the warmth to deplete. And if the warmth is generated speedier than it dissipates, then the appliance gets warmer.