Your cell phone typically consumes about 420 mW of power when you text a friend.

Question

Your cell phone typically consumes about

420 mW

of power when you text a friend. If the phone is operated using a lithium-ion battery with a voltage of

3.7 V,

what is the current flowing through the cell-phone circuitry under these circumstances?
A

Compare your result with the data given in the table below.

a. The current in the cell phone is less than a spark plug but greater than a calculator.

b. The current in the cell phone is less than a color television but greater than a 60-watt lightbulb.    

c. The current in the cell phone is less than an 1800-watt hair dryer but greater than a color television.

d. The current in the cell phone is less than a clock radio but greater than a spark plug.

e. The current in the cell phone is less than a 60-watt lightbulb but greater than a clock radio.

Explanation / Answer

P = 420 mW
P = 0.42 W

V = 3.7 V

We know,
P = V*I
0.42 = 3.7 * I
I = 0.42/3.7
I = 0.114 A

Correct option:- (e) The current in the cell phone is less than a 60-watt lightbulb but greater than a clock radio.

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