(a) The resistance of a wire of 0.01 cm radius and 1.0 cm length is 7 Ω. Calculate its resistivity.
(a) The resistance of a wire of 0.01 cm radius and 1.0 cm length is 7 Ω. Calculate its resistivity.
Solution
(a) r = 0.01 cm=1 × 10-4 m
𝑙 = 1 cm = 0.01 m
𝑙
R =
A
RA 𝑅 x 𝜋𝑟 2
= 𝑙 = 𝑙
7 x 22 × 10−8
= 7 x 0.01
= 22 × 10-8 x 102
= 22 × 10-6 Ωm =2.2 × 10-5 Ωm
OR
V
(b) Resistance of electric heater R =
I
R = 11
R = 20 Ω
V2
P =R
200 x 200
P = 20
P = 2000W/ 2 kW
PAGE 8 {31/1/1}