If a refrigerator is connected to a branch circuit rated at...

If a refrigerator is connected to a branch circuit rated at 20 A and that branch circuit supplies additional devices, what's the maximum current the refrigerator can require in this circuit? A. 14 A B. 10 A C. 16 A D. 12 A

Transcript

00:01 So we have some givens.

00:01 We have a current through the wire of 18 amps.

00:05 We have a voltage equaling 220 volts.

00:12 And then we have a diameter of the wire, 1 .628 millimeters.

00:18 We can say that the radius is going to be 0 .814 times 10 to the negative 3rd meters.

00:27 We can say the length is equal to 3 .5 meters as well.

00:31 So for part a, they're asking for the power.

00:33 We know the power is simply the product of the current times of voltage.

00:37 So here it's going to be 18 times 220.

00:41 And we're looking at 3 ,960 watts.

00:49 At this point, for part b, we can see the power dissipated.

00:53 And this is going to equal i squared times the resistance.

00:58 The current square times the resistance.

01:00 This is going to be i squared times the resistivity of copper, times the length of the wire divided by the cross -sectional area of the wire.

01:09 And this is going to be equal to i squared times the resistivity of the copper times the length divided by pi r squared.

01:20 Now for this we can solve.

01:23 So the power dissipated is going to be 18 squared times the resistivity of copper, 1 .68 times 10 to the negative 8 oms meters.

01:36 And then we'll have 3 .5 and then divided by pi 0 .814 times 10 to the negative third, and this will be squared.

01:51 So the power dissipated is going to be equal to approximately 18 .3 watts.

02:00 So not too much...

Question

If a refrigerator is connected to a branch circuit rated at 20 A and that branch circuit supplies additional devices, what's the maximum current the refrigerator can require in this circuit? A. 14 A B. 10 A C. 16 A D. 12 A

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