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Question
In the circuit shown in fig., find the reading of the ammeter A when the switch S is opened.
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Solution
When the switch S is opened, resistance 60Ω is not connected in the circuit and current flows through the 20Ω resistor.
∴ Resistance of the circuit. when the switch is open:
R = 20 + 5
= 25 Ω
Given, voltage = 10 V
∴ Current through the circuit,
I = `V/R`
= `10/25`
= 0.4 A
The reading of the ammeter is thus 0 .4 A, when the switch is open.
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