An aluminium wire `7.5 m` long is connected in parallel with a copper wire `6 m` long. When a current of `5 A` is passed through the combination, it is found that the current in the aluminium wire is `3 A`. The diameter of the aluminium wire is `1 mm`. Determine the diameter of the copper wire. Resistivity of copper is `0.017 muOmega-m` and that of the aluminium is `0.028 muOmega-m`.

Explanation

To determine the diameter of the copper wire, we can follow these steps:

### Step 1: Understand the given data
- Length of aluminium wire, \( L_A = 7.5 \, \text{m} \)
- Length of copper wire, \( L_C = 6 \, \text{m} \)
- Total current, \( I_{total} = 5 \, \text{A} \)
- Current through aluminium wire, \( I_A = 3 \, \text{A} \)
- Current through copper wire, \( I_C = I_{total} - I_A = 5 \, \text{A} - 3 \, \text{A} = 2 \, \text{A} \)
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