Question

Two wires A and B of equal length and circular cross section are made of the same metal, but the resistance of wire B is four times that of wire A. What is the ratio between their spokes ?: a) rB / rA = 2, b) rA / rB = 2, c) rB / rA = 4, d) rA / rB = 16

Answer 1

Option B is the correct answer.

Step-by-step explanation:

We have resistance
`R=(\rho l)/(A)`

The resistance of wire B is four times that of wire A

`R_B=4R_A\\\\(\rho_B l_B)/(A_B)=4* (\rho_A l_A)/(A_A)\\\\(A_A)/(A_B)=4\\\\(\pi r_A^2)/(\pi r_B^2)=4\\\\(r_A)/(r_B)=2`

Option B is the correct answer.