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प्रश्न
The emf of a standard cell is 1.5V and is balanced by a length of 300 cm of a potentiometer with a 10 m long wire. Find the percentage error in a voltmeter that balances at 350 cm when its reading is 1.8 V.
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उत्तर
Given:
E1 = 1.5 V, l1 = 300 cm, l2 = 350 cm
From individual cell method of potentiometer,
`"E"_1/"E"_2 = "l"_1/"l"_2`
∴ E2 = E1 × `"l"_2/"l"_1`
= `1.5 xx 350/300 = 1.75`V
But given reading is 1.8 V
∴ Error = 1.8 – 1.75 = 0.05 V
∴ Percentage error = `0.05/1.75 xx 100`
= 2.8571%
The percentage error in a voltmeter is 2.8571%.
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