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A voltmeter reads the potential differen...

A voltmeter reads the potential difference across the terminals of an old battery as `1.40 V`, while a potentiometer reads its voltage to be `1.55 V`. The voltmeter resistance is `280 Omega`.

A

The emf of the battery is `1.4 V`.

B

The emf of the battery is `1.55 V`.

C

The internal resistance `r` of the battery is `30 Omega`

D

The internal resistance `r` of the battery is `5 Omega`

Text Solution

Verified by Experts

The correct Answer is:
B, C
The potential measures the exact value of emf of a battery.
Therefore, `E = 1.55 V`.
Also, `1.4=I(280)` or `I=0.005 A`
Also, `1.4 = I(280)`or `I = 0.005 A`
Also, `V = E - Ir` or `r = ((E - V))/(I) = (1.55 - 1.40)/(0.005) = 30 Omega`
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Knowledge Check

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