Question

Uniform wires of resistance 100 omes are melted and recast into wire of length double that of the original. What would be the resistance of the new wire formed

Answer 1

Explanation:

R is resistance in ohm, ρ is resistivity in ohm-meter, l is length in meter & A is cross sectional area in m^2

R = ρ*l/A

where ,

Since the current becomes ‘2l’ & the ‘A’ becomes ‘A/2’, so the new resistance will be,

R’ = ρ*2l/(A/2)

or, R’ = ρ*2*2*l/A

or, R’ = 4*ρ*l/A

or, R’ = 4R