MCQ
Two wires that are made up of two different materials whose specific resistance are in the ratio $2 : 3$, length $3 : 4$ and area $4 : 5$. The ratio of their resistances is
- A$6:5$
- B$6:8$
- ✓$5:8$
- D$1:2$
✓
Answer
Correct option: C.
$5:8$
c
(c) Resistance $ = \rho \frac{l}{A}$
(c) Resistance $ = \rho \frac{l}{A}$
$\therefore $ $\frac{{{R_1}}}{{{R_2}}} = \frac{{{\rho _1}}}{{{\rho _2}}} \times \frac{{{l_1}}}{{{l_2}}} \times \frac{{{A_2}}}{{{A_1}}} = \frac{2}{3} \times \frac{3}{4} \times \frac{5}{4} = \frac{5}{8}$
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