When the lights of an automobile are switched on, an ammeter in series with them
ID: 2194863 • Letter: W
Question
When the lights of an automobile are switched on, an ammeter in series with them reads 10.20 A and a voltmeter connected across them reads 12.10 V. When the electric starting motor is also turned on, the ammeter reading drops to 9.00 A and the lights dim somewhat. If the internal resistance of the battery is 42 m? and that of the ammeter is negligible, what is the emf of the battery?
----Answer: 12.53v
What does the voltmeter read when the starting motor is turned on?
What is the current through the starting motor?
Explanation / Answer
A) ?v = e - Ir e = ?v + Ir e = 12.1V + (10.2A)×(.042O) =12.52 v answer B)if you start off 10.20 A and ended up with 9 A... it means the other 1.2A went through the motor.
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