1. A power supply with internal resistance of 4 ? applies a voltage of 14 V. If
ID: 2134714 • Letter: 1
Question
1. A power supply with internal resistance of 4 ? applies a voltage of 14 V. If a load resistor of 40 ? is in series with the power supply, then what is the current going through the circuit? Express the answer with two decimal places.
2. A 74 W light bulb with a resistance of 177 ? is connected to a power supply with a 119 V. What is the internal resistance of the power supply? Express the answer with one decimal place.
3. Find the resistance of a 11 meter length of metal wire of 0.4 mm diameter. The resistivity of metal is 2.6
Explanation / Answer
1)
A power supply with internal resistance of 4 ? applies a voltage of 14 V to a load resistor of 40 ? in series with the power supply.
14V / 40 ohms = 0.35A
The internal resistance will also experience the same current, and have a voltage drop of
V = 4 * 0.35 = 1.40V
2)
Total circuit current = 74W / 119V = 0.622A
Total circuit resistance = 119V / 0.622A = 191.32 Ohm
Power supply resistance = 191.32 - 177 = 14.32 Ohm.
3)
Resistivity is in ?
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