Discussion :: Network Analysis and Synthesis
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The frame of electric motor is connected to three plates having earthing resistance of 10 Ω, 20 Ω and 30 Ω respectively. The materials of the three plates are copper, aluminium and iron respectively. The percentage of energy dissipated by 10 Ω earthing plate
A.
is more than 50% of total energy
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B.
is less than 50% of total energy
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C.
depends on the materials of the three plates
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D.
may be more or less than 50% of total energy
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Answer : Option A
Explanation :
The parallel combination of 30 Ω and 20 Ω is 12 Ω. Since 12 Ω and 10 Ω are in parallel, the 10 ohm plate draws more than 50% current and dissipates more than 50% energy.
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