In a metre-bridge experiment, a known resistance $R = 5\ \Omega$ is in the right gap. The balance length on the wire is $\ell_x = 40$ cm (measured from the left end). The unknown resistance $X$ in the left gap is:
A10.0 Ω
B7.50 Ω
C5.0 Ω
D3.33 Ω
Answer & Solution
Correct answer: D. 3.33 Ω
Metre bridge: $X/R = \ell_x/\ell_R = 40/60 = 2/3$ ⇒ $X = (2/3)(5) = 3.33\ \Omega$.
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