In a series electrical cicuit comprising a resistor made up of metallic wire, the ammeter reads 100mA. If the length of the wire is doubled, how will the current in the circuit change? Justify your answer.

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Solution

When the length of the wire is doubled, the resistance is also doubled, because resistance is directly proportional to the length of the wire. Hence according to ohms law for a given potential difference, the current reduces to half.

Before length is doubled

I=V/R= 100mA

when Length is doubled resistance also gets doubled.
$I^{'} = V / 2 R$

$I^{'} = I / 2$
$I^{'} = 100 m A / 2$
$I^{'} = 50 m A$

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