Question

Q5. A copper wire has diameter 0.5mm and resistivity of 1.6 x 10 ohm m. What will be the length of this wire to
make its resistance 10ohm? How much does the resistance change of diameter is doubled?​

Answer 1

Answer:

Given,

diameter of copper wire = 0.5mm = 5 × 10-⁴ m

resistivity = 1.6 × 10^-8 ohm.m

resistance = 10 ohm

Length = ?

we know,

R = dL/A

where R , d , L and A are resistance , resistivity , length and cross section area.

10 = 1.6 × 10^-8 × L/(πr²)

L = 10 × 3.14 × (2.5 × 10^-4)² × 10^8/1.6

L = 10× 3.14 × 6.25/1.6

L = 122.656 m.

If the diameter of the wire is doubled, new diameter=2×0.5=1mm=0.001m

Let new resistance be Rʹ

∴ The new resistance is 2.5 Ω

♥️Hope it will be helpful.♥️