Question

A conductor of resistance 20 Ω is cut into n equal parts. All the parts are bundled together in parallel. The equivalent is obtain as $\frac{1}{5}$Ω. The number of parts is –

• A. n = 2
• B. n = 4
• C. n = 8
• D. n = 10

Answer 1

Answer: (D)

n = 10

Answer 2

when wire is cut into 'n' parts then resistance of each part becomes r = R/n

When they are connected in parallel R_eq = $\frac{r}{n}$

R_eq = $\frac{r}{n}$ = $\frac{R}{n^{2}}$ ; $\frac{1}{5}$ =$\frac{20}{n^{2}}$ ; ∴ n²= 100 ⇒ n = 10 parts