Question

In the given circuit, connect a nichrome wire of length ‘L’ between points X and Y and note the ammeter reading.

(i) When this experiment is repeated by inserting another nichrome wire of the same thickness but twice the length (2L), what changes are observed in the ammeter reading?

(ii) State the changes that are observed in the ammeter reading if we double the area of cross-section without changing the length in the above experiment. Justify your answer in both the cases.

Answer 1

(i) The ammeter reading will decrease. This is because Resistance is directly proportional to the length; hence with the increase in the length the resistance of the wire will increase. So the current will decrease due to increase in the resistance (current is inversely proportional to the resistance). 

(ii) The ammeter reading will increase because. R = ρ\(\frac1A\)

Thus the resistance is inversely proportional to the area of the cross section, so with the increase in the area the resistance of the wire will decrease. 

Therefore with the decrease in the resistance the current will increase (current is inversely proportional to the resistance).hence the ammeter reading will increase