The balancing length for R (when 1,2 are connected) be is l1 and balancing length for R+X (when 1,3 is connected is l2 ) Then iR=kl1 and i(R+X)=kl2 Given i=1 A R=kl1R+X=kl2 Subtracting Eq. (i) from Eq. (ii), we get X=k(l2−l1)
NEET UG 2010 — Physics Electromagnetism
2010mcqhard
A potentiometer circuit is set up as shown. The potential gradient across the potentiometer wire, is k volt/cm and the ammeter, present in the circuit, reads 1.0 A when two way key is switched off. The balance points, when the key between the terminals (i) 1 and 2 (ii) 1 and 3 , is plugged in, are found to be at lengths l1 cm and l2 cm respectively. The magnitudes, of the resistors R and X, in ohm, are then, equal, respectively, to 
Official previous-year question
Held on 30 Apr 2010 · Verified 9 Jul 2026.
Options
- A
k(l2−l1) and kl2
- B
kl1 and k(l2−l1)
- C
k(l2−l1) and kl1
- D
kl1 and kl2
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