Will the terminal voltage of the battery increase, decrease or remain the same?

Question

If another resistor is added to the circuit, between the positive terminal of the battery and the two of 6.0 Ω parallel resistors, will the terminal voltage of the battery increase, decrease or remain the same? Use principles of physics to explain your answer.

Answer 1

Hard to answer without seeing the circuit, but...

If the internal resistance of the battery is not zero, the terminal voltage (Vt) depends on the current draw. If there is no current, Vt = EMF. Because of internal resistance, a bad battery with high internal resistance can have a 12v reading (open circuit) but give much less than 12V once current flows.

Vt = E - Ir

where E is the EMF and I is the current in the circuit.

If the overall current is dropping because a resister is being added in series to existing net resistance, then this reduces the current draw, hence Vt increases, because the Ir term is getting smaller.

Answer 2

Michael

lt will stay the same. The terminal voltage of the battery determines the amount of energy an electron has leaving the - terminal moving to the + terminal. (1 V = 1 J/C). That is a fixed property of the battery, the amount of resistance in the circuit is irrelevant.

The current is a measure of the speed of the electrons in the circuit. Ohm's Law V=IR for a series circuit shows that if R increases, I decreases as V is fixed (by the voltage of the battery).

So adding a resistor would decrease the current in the circuit.

Mike