A battery of EMF 12 volts and internal resistance 2 ohms is connected to an external resistor. If the current in the circuit is 2 amperes, what is the value of the external resistance?

C. 4 , — Using Ohm's law for a complete circuit, the total EMF is equal to the product of the current and the total resistance of the circuit. The total resistance is the sum of the external and internal resistances.

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$A battery of EMF ε = 12 V and internal resistance r = 2 Ω is connected to an external resistor R . If the current in the circuit is I = 2 A, what is the value of the external resistance R ?$

A. $2 Ω$
B. $6 Ω$
C. $4 Ω$
D. $8 Ω$

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Correct answer: C — $4 Ω$

Solution

Using ε = I (R + r), we have $12 = 2(R + 2)$. Dividing by 2 gives $6 = R + 2$, so R = 4 Ω .

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A battery of EMF ε=12V and internal resistance r=2Ω is connected to an external resistor R. If the current in the circuit is I=2A, what is the value of the external resistance R?

Solution

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More Current Electricity practice questions

$A battery of EMF ε = 12 V and internal resistance r = 2 Ω is connected to an external resistor R . If the current in the circuit is I = 2 A, what is the value of the external resistance R ?$