- #1
pp280
- 2
- 0
The setup shows a Galvanic cell connected to a voltmeter. The question asks how the reading of the voltmeter would change if the voltmeter's resistance became finite (instead of infinite) and current started to pass through the voltmeter.
The answer given is "The reading will decrease because the voltage decreases as the current increases"
I've tried drawing circuit diagrams to show this, but I'm stuck. Here's how I approach the problem:
First, I draw a circuit with a battery and a single resistor. The galvanic cell is the voltage source and I assume there is some internal resistance in the circuit. Since the voltmeter initially has infinite resistance, I leave it out.
When the voltmeter shorts, that's like adding another resistor in parallel. However, I don't see why this would change the voltage measurement. Adding a resistor in parallel decreases the total resistance of the circuit, and causes the total current to increase. BUT isn't it the case that while the total current in the circuit is greater than before, it splits in such a way that the same voltage drop occurs across both resistors?
As far as the given answer's reference to voltage decreasing as current increases, that sounds like P= IV, but I can't see how that would enter the picture.
Would appreciate any help!
The answer given is "The reading will decrease because the voltage decreases as the current increases"
I've tried drawing circuit diagrams to show this, but I'm stuck. Here's how I approach the problem:
First, I draw a circuit with a battery and a single resistor. The galvanic cell is the voltage source and I assume there is some internal resistance in the circuit. Since the voltmeter initially has infinite resistance, I leave it out.
When the voltmeter shorts, that's like adding another resistor in parallel. However, I don't see why this would change the voltage measurement. Adding a resistor in parallel decreases the total resistance of the circuit, and causes the total current to increase. BUT isn't it the case that while the total current in the circuit is greater than before, it splits in such a way that the same voltage drop occurs across both resistors?
As far as the given answer's reference to voltage decreasing as current increases, that sounds like P= IV, but I can't see how that would enter the picture.
Would appreciate any help!