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| Numerical 15 |
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| 15. Two straight wires A and B of lengths 10m and 12m carrying currents of 4.0A and 6.0A respectively in opposite directions lie parallel to each other at a distance of 3.0cm. Estimate the force on a 15cm section of the wire B near its centre. |
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| Suggested solution: |
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| The ratio of the length of the wires to the separation between them is large (more than 300). Therefore, one can estimate the approximate force on a section of either of the two wires (near their centres) by using the exact result for force per unit length for two infinitely long wires carrying currents I1 and I2. |
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| Force per unit length |
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| Force on 15cm section of wire B (near it's centre) |
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| = 1.6 x 10-4 x 0.15 N |
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| = 2.4 x 10-5 N |
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Moving Charges and Magnetism
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