During an experiment with a metre bridge, the galvanometer shows a null point when the jockey is pressed at 40.0 cm using a standard resistance of 90 Ω, as shown in the figure. The least count of the scale used in the metre bridge is 1 mm. The unknown resistance is

Engineering

Physics

Errors

Galvanometer Ammeter and Voltmeter

Question

During an experiment with a metre bridge, the galvanometer shows a null point when the jockey is pressed at 40.0 cm using a standard resistance of 90 Ω, as shown in the figure. The least count of the scale used in the metre bridge is 1 mm. The unknown resistance is

135 ± 0.23 $Ω$

135 ± 0.56 $Ω$

60 ± 0.25 $Ω$

60 ± 0.15 $Ω$

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$\frac{R}{90} = \frac{40}{60}$

$R = 60 Ω$

$\frac{ΔR}{R} = \frac{Δℓ}{ℓ (1 - ℓ)}$

$ΔR = \frac{60 \times 10^{- 3}}{0 .4 \times 0 .6} = 0 .25 Ω$