**Resistance of a Heater**

Part A = 12.5 A

Part B = 9.6 ohms

Part C = 16.1 minutes

**Solutions Below:**

Part A

Express your answer for the current numerically, to three significant figures.

The formula for power is W = I^{2} * R. The problem doesn’t give us either of these, but we know that V = IR, so we can substitute:

W = I^{2} * R

W = I * V

1500 = I * 120

I = 12.5 A

Part B

Express your answer numerically, to three significant figures.

The formula for power is W = I^{2} * R. The current from part A is 12.5 A, so just subsitute:

W = I^{2} * R

1500 = (12.5)^{2} * R

1500 = 156.25 * R

R = 9.60 ohms

Part C

^{3}.

Express your answer numerically in minutes, to three significant figures.

The room is 3.00 x 5.00 x 8.00 = 120m^{3}. So there is 144 kg of air in the room (1.20 kg/m^{3} * 120m^{3}). This means it takes 144 * (10.0 * 1006) = 1448640 J of energy to raise the temperature by 10 degrees. At 1500 W (1 J/s) it will take 1448640 / 1500 = 965.76 seconds, or 16.1 minutes (965.76 / 60).

t = 16.1 minutes