An automobile battery has an emf of 12.60 V and an internal resistance of 0.076

Question

An automobile battery has an emf of 12.60 V and an internal resistance of 0.076 0 ?. The headlights together have an equivalent resistance of 6.400 ? (assumed constant). (a) What is the potential difference across the headlight bulbs when they are the only load on the battery? (Give your answer to four significant figures.) __________ V (b) What is the potential difference across the headlight bulbs when the starter motor is operated, requiring an additional 35.0 A from the battery? (Give your answer to four significant figures.) _______________ V

Explanation / Answer

a. current through load=12.6/(0.076+6.4)=1.945 A so potential difference across the headlight bulb=1.945*6.4=12.448 volts b. potential difference across headlight will remain the same coz only way to derive an additional 35 A from the battery,is to connect the starter motor in parallel with the headlight bulb. let now the voltage across the parallel load be V. total current =35+1.945=36.945 A then this amount of current passes through the internal resistance of the battery. so (12.6-v)/0.076=36.945 so v=9.792 volt

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