Q When a potential difference of 2V is applied across the ends of a wire of 5m length a - Science - Electricity

Question

Q When a potential difference of 2V is applied across the ends of a
wire of 5m length a current of 1A is found to flow through it
Calculate
(i) The resistance per unit length of the wire
(ii) The resistance of 2m length of this wire
(iii) The resistance across the ends of the wire if it is doubled
on itself

Akash · Answer

By Ohm's law, V = iR
R = V/i = 2/1 = 2 Ω (1)
(i) Resistance per unit length of wire = 2/ 5 = 0 4 Ω/m
(ii) Resistance of 2 m length of wire = 2 * 0 4 = 0 8 Ω
(iii) We know, R = ρl/A
When wire is doubled on itself, length becomes half and cross
section area of wire is doubled
l' = l/2, A' = 2A
Now R' = ρl/4A or R' = R/4 = 2/4 = 0 5 Ω [See equation 1]