In a DC circuit, a 12 V battery with internal resistance r = 1 ohm is connected across a resistor R = 5 ohms. What is the terminal voltage across the battery?
Answer and explanation
Correct answer: A. 10.0 V
- Step 1: Total resistance of the circuit: R_{tot} = R + r = 5 + 1 = 6 ohms.
- Step 2: Circuit current: I = E / R_{tot} = 12 / 6 = 2 A.
- Step 3: Voltage drop across internal resistance: V_{drop} = I r = 2 1 = 2 V.
- Step 4: Terminal voltage: V = E - Ir = 12 - 2 = 10 V (or V = I R = 2 * 5 = 10 V).
Answer
10.0 V.
Why not the others: 12.0 V assumes an ideal battery with zero internal resistance; 2.0 V is the internal voltage loss, not the terminal voltage; 6.0 V assumes r = R.
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