A transformer for charging a power tool steps the line voltage down to 2.9 V.
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# A transformer for charging a power tool steps the line voltage down to 2.9 V.

[From: ] [author: ] [Date: 11-07-07] [Hit: ]
that would be great!-Output power is 2.9 volts x 240 ma = 0.input power is 0.696 watts / 0.8 = 0.......
The output current of this transformer is 240 mA. If the transformer is 80% efficient, what is the input current?
A)7.3 mA
B)240 mA
C)4.6 mA
D)190 mA
E)300 mA

If you could walk me through the steps, that would be great!

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Output power is 2.9 volts x 240 ma = 0.696 watts
input power is 0.696 watts / 0.8 = 0.87 watts

assuming 120 volts line voltage, input current is 0.87 watts / 120 = 7.25 mA (a)

If the line is 240 volts, input current is 3.63 mA

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