Question

Four wires made of same material have different lengths and radii. The wire having more resistance in the following is

• A. l = 100 cm r = 1 mm
• B. l = 50 cm r = 2 mm
• C. l = 100 cm r = 1/2 mm
• D. l = 50 cm r = 1/2 mm

Answer 1

The correct option is C l = 100 cm r = 1/2 mm

$R\propto \frac{l}{r^2}$

a) $\frac{l}{r^2}=\frac{100}{\frac{1}{100}}=10000$

b) $\frac{l}{r^2}=\frac{5000}{4}=1250$

c) $\frac{l}{r^2}=\frac{100}{\frac{1}{400}}=40000$

d) $\frac{l}{r^2}=\frac{50}{\frac{1}{400}}=20000$

$\Rightarrow moreresistance$