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

Step-by-step solution

The unknown resistance is given by, R = x 100 - x 90 Putting x = 40 . 0   cm , R = 60   Ω For error analysis, R = 40 . 0 ± 0 . 1 100 . 0 - 40 . 0 ± 0 . 1 × 90 = 40 . 0 ± 0 . 1 60 . 0 ± 0 . 1 × 90 In multiplication and division, fractional errors get added up. Therefore, ∆ R R = 0 . 1 40 + 0 . 1 60 ⇒ ∆ R = 100 40 60 × 0.1 × 60 = 0.25   Ω Hence, R = 60 ± 0 . 25   Ω