A battery of e.m.f 3.0V is connected across a potentiometer wire AB of length 10Ωm‾¹ as illustrated in the diagram above. If the jockey J makes contact at the 30cm mark, determine the resistance of length AJ and voltage across AJ.

A. 3.0Ω; 0.9V
B. 3.0Ω; 3.0V
C. 3.3Ω; 0.3V
D. 3.3Ω; 9.0V

Correct Answer: Option A

Explanation

E = 3.0V; R/l=10Ωm‾¹
l = 30cm = 0.3m; R = 10Ωm‾¹ × 0.3m=3Ω
E/V=l1/l2 ⟹ 3/V = 1/0.3
= 3×0.3/1 =0.9V