9A
YOUR ANSWER: 10 watts.
Good. You are remembering that P = E x I in our basic power formula. When current flows in a
resistance, heat is produced. The heat energy is evidence that power is used in producing current in a
resistance. The power is generated by the source of applied voltage and consumed in the resistance in
the form of heat.
It is convenient, then, to have a power formula to express power in watts in terms of resistance.
For current:
P = I2R.
For voltage:
P = E2.
R
P = E x I = 6 x 2 = 12 watts.
P = I2R = 4 x 3 = 12 watts.
P = E2 = 36 = 12 watts.
R
3
If you knew the voltage and resistance in a circuit, which formula would you use to solve for
power?
P = E2.
frame 4B
R
P = E x I.
frame 7B
9B
YOUR ANSWER: 750 watts.
Again, we answer your answer with, not quite.
The formula again is P I2R, not P = IR; you forgot to square I in your solution.
Go back to frame 11A and try again.
IT0348
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