Emf balanced by a length of potentiometer wire with a given potential difference across the wire

The same question, asked 4 times: 26 Apr 2025 S1*, 13 Apr 2026 S1, 15 Apr 2026 S2*, 16 Apr 2026 S1. Every wording below, oldest first.

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Question 1
26 Apr 2025 S1
40 $The potentiometer wire is 5 m long and potential difference of 4 V is maintained between the ends. The e.m.f. of the cell which balances against a length of 200 cm of the potentiometer wire is$
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Question 2
13 Apr 2026 S1
129 $A potentiometer wire is 4 m long and potential difference of 3V is maintained between the ends. The e.m.f. of the cell which balances against a length of 100 cm of the poteniometer wire is$
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Question 3
15 Apr 2026 S2
130 $A potentiometer wire is 4m long and potential difference of 2V is maintained between the ends. The e.m.f. of the cell which balances against a length of 80 cm of the potentiometer wire is$
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Question 4
16 Apr 2026 S1
129 $A potentiometer wire is 4m long and potential difference of 3V is maintained between the ends. The e.m.f. of the cell which balances against a length of 100 cm of the potentiometer wire is$
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Question 1