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.
$5: 8$
($ \text { 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}$
$ \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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