Question

5. A copper wire has a diameter of 0.5 mm and a resistivity of 1.6 x 10-6 ohm cm. How much of this
wire would be required to make a 10 ohm coil ? How much does the resistance change if the
diameter is doubled ?​

Answer 1

Answer:

We are given that, diameter of the wire, D=0.5mm=0.5×10−3m

resistivity of copper, ρ=1.6×10−8ohmm

required resistance, R=10ohm

As R=ρlA,l=RAρ=R(πD2/4)ρ=πRD24ρ[A=πr2=π(D/2)2=πD2/4].

or l=3.14×10×(0.5×10−3)24×1.6×10−8m=122.7m

Since, R=ρlπD2/4=4ρlπD2,R∝1/D2. When D is doubled, R becomes 14 times.

Explanation: