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The masses of the three wires of copper are in the ratio of 1 : 3 : 5 and their lengths are in the ratio of 5 : 3 : 1. The ratio of their electrical resistance is
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- 1 : 3 : 5
- 5 : 3 : 1
- 1 : 25 : 125
- 125 : 15 : 1
Correct Option: D
| R = | ρ l | . But m = πr²ld ∴ πr² = | m | |
| πr² | ld |
| ∴ R = | ρl²d | ,R1 = | ρl1²d | ,R2 = | ρl2²d | ||
| m | m1 | m2 |
| R3 = | ρl1²d | |
| m3 |
| R1 : R2 : R3 = | 25 | : | 9 | : | 1 | = 125 : 15 :1 | |
| 1 | 3 | 5 |
