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Grade 10Electric Current

A high resistance voltmeter is connected to a dry cell battery. The voltmeter reads 12v when the circuit is open and when a 24 ohm resistance is connected across the battery terminals the voltmeter reads 7.2 volt. Find internal resistance.

Harshini

9 Years agoGrade 10

1 Answer

deepak

9 Years ago

since the voltmeter reads 12v in a open circuit the EMF(E) of the cell is 12v

but when a resistance(R) =24 ohm is connected then the terminal voltage(T_v) of the cell is measured to be 7.2v

let the internal resistance be r,

then by formula,

r=R(E/T_v)−R ….….….….if you dont know this formula then check the expression for internal resistance of a cell expression in google

substituting the values ,

r=16 ohm

P.S. are you really 10^th cause this is an 12^th standard problem

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