Published by :
Renji Elsa Jacob, M-Tech in Electrical & Electronics Engineering
1.A coil consists of 1000 turns of copper wire having a cross-sectional area of 0.8mm2. The mean length per turn is 80cm and the resistivity of copper is 0.02µΩ-m. Find the resistance of the coil and the power absorbed by the coil when connected across 100V dc supply?
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- Find the resistance of 1000 metres of a copper wire 20 sq.mm in cross-section. The resistance of copper is 1/56 ohm per metre length and 1 sq.mm cross-section. What will be the resistance of another wire of the same material, three times as long and one-half area of cross-sectional.
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3. A lead wire and an iron wire are connected in parallel. Their respective specific resistances are in the ratio 47:30. The former carries 80 percent more current than the latter and the latter is 48 percent longer than the former. Determine the ratio of their cross-sectional areas.
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4. A 16 Ω resistor is connected to a 8V battery. What will be the current flowing in the resistor?
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5. A current of 100mA flows in a 65 Ω resistor. What voltage drop (potential difference) will be developed across the resistor?
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6. A voltage drop of 25V appears across a resistor in which a current of 1mA flows. What is the value of resistance?
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7. A 100V lamp has a hot resistance of 255Ω. Find the current taken by the lamp and its power rating in watts. Calculate also the energy it will consume in 24 hours.
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