Question

A student while performing the experiment to find the resultant resistance of two resistors connected in series observed the ammeter pointer at position P when the key is 'off' and the same pointer at position Q when the key is 'on'.



The correct reading of ammeter is:
(1) 0.2 A
(2) 2.5 A
(3) 2.3 A
(4) 2.7 A

Answer 1

Least count of the given scale = 0.1 A

Main scale reading $=25\times 0.1\text{A=2.5 A}$

Zero error = $2\times 0.1=0.2\text{A}$

True reading of the ammeter = Main scale reading - Zero error = 2.5 A $-$ 0.2 A = 2.3 A

Hence, the correct answer is option 3.