In a meter bridge experiment with a 100 cm long uniform wire, an unknown resistance X is connected in the left gap and a known resistance of 10 is connected in the right gap. If the galvanometer shows a null deflection when the jockey is placed at a distance of 25 cm from the right end of the bridge wire, the value of the unknown resistance X is:

Step-by-step solution

In a meter bridge, the balancing condition is given by R₁ l₁ = R₂ l₂ , where l₁ and l₂ are the balancing lengths from the left and right ends respectively. Given that the balance point is at 25 cm from the right end, we have l₂ = 25 cm . The length from the left end is l₁ = 100 - 25 = 75 cm . The resistance in the right gap is R₂ = 10 . Let the unknown resistance in the left gap be X . Applying the balancing condition: X 75 = 10 25 X = 75 10 25 = 3 10 = 30 Answer: 30