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A resistor is connected in series with a power supply of 35 volts, producing a current in the resistor of 0.25 amps.
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What is the resistance of the resistor?
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If we draw a sketch of this circuit, we know it has a resistor, whose value we’ll call 𝑅, in series with the power supply of 35 volts.
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Along with that, we’re told that a current 𝐼 of 0.25 amps runs through this series circuit.
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The question is what is the resistance of this resistor?
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To figure it out, we can rely on Ohm’s law, which tells us that the potential difference in this circuit is equal to the product of the resistance times the current.
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We’ll treat this circuit as that the only source of resistance in it is the resistor 𝑅.
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That is, we’ll assume there’s no resistance in the wires of the circuit and that there’s no internal resistance in the power supply.
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Under that assumption and using Ohm’s law in a rearranged form, we can say that the resistance of the resistor is equal to the potential difference 𝑉 divided by the current in the circuit 𝐼.
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35 volts divided by 0.25 amps is equal to 140 ohms.
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That’s the resistance value of the resistor in this circuit.