Question

A 1 ohm resistance is in series with an ammeter which is balanced by 75 cm of potentiometer wire. A standard cell of 1.02v is balanced by 50 cm.The ammeter shows a reading of 1.5A. The error in the ammeter reading.​

Answer 1

Let the resistance of ammeter be r.

Therefore in balancing condition,

I(r+1) = k×0.75 _ _ _ _ _ _(1)

and 1.5 (r+1) = k×0.50 _ _ _ _ _ _(2)

From eqns (1) and (2), we get,

I(r+1) = 1.5 (r+1)/0.50 × 0.75

or I = 4.5

Therefore the difference between the readings of ammeter is given by,

error in ammeter = 4.5 - 1.5 = 3.0 A.