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| Numerical 02 |
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| 02. A wire 40 cm long bent into a rectangular loop of 15 cm x 5 cm is placed perpendicular to the magnetic field whose flux density is 0.8Wbm2. Within 0.5 seconds, the loop is changed into a 10cm square and the flux density increases to 1.4 Wb m-2. Find the induced EMF. |
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| Suggested solution: |
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| Initial area, |
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| A1 = 15 cm x 5 cm = 75 cm2 = 75 x 10-4 m2 |
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| Initial magnetic flux density, |
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| B1 = 0.8 Wb m-2 |
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| Initial magnetic flux, |
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| f1 = B1A1 = 0.8 x 75 x 10-4 Wb = 60 x 10-4 m2 |
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| Final area, |
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| A2 = 10cm x 10 cm = 100cm2 = 100 x 10-4 Wb |
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| Final magnetic flux density, |
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| B2 = 1.4 Wb m-2 |
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| Final magnetic flux, |
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| f2 = B2A2 = 1.4 x 100 x 10-4 Wb |
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| = 140 x 10-4 Wb |
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| Change in magnetic flux, |
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| df = f2 - f1 = (140 x 10-4 - 60 x 10-4 ) Wb |
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| Induced EMF |
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