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esha
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They are pushing in opposite directions and balance out at the null point.esha said:View attachment 207224 this is the potentiometer and the emf of cell E2 is unknown. now to know the emf just finding the null point of the galvanometer is enough. its because at that given length the potentiometer has the same potential as the cell. but why are they equal at null point?
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I'm not quite getting the question. The problem is that we do not know the relationship between the resistor in the upper circuit and the resistance of the potentiometer between ends A and B. or is that relationship given? That voltage divider will determine the null point for the potentiometer wiper, and without that relationship I don't think much can be said...esha said:potentiometer and the emf of cell E2 is unknown. now to know the emf just finding the null point of the galvanometer is enough. its because at that given length the potentiometer has the same potential as the cell. but why are they equal at null point?
You're not being stupid. I'm having a conceptual problem with this as well, but I think it's because the circuit is non-physical with zero resistance in the bottom loop. An ideal voltage source and an ideal galvanometer each have zero internal resistance, so the problem is poorly formulated, IMO.esha said:i got it but why is there no potential difference in the bottom loop? sorry if i m being too stupid
Correct.esha said:then if its correct E2 = I2R1.
No, E2 is a voltage. The current through the bottom leg is zero at the null point.esha said:this means at null point E2 = 0
The null point is where there is no Potential Difference - that's why no current flows through the meter.esha said:but why are they equal at null point?
esha said:but if the batteries are present what prevents them from supplying current?
sophiecentaur said:The null point is where there is no Potential Difference
If you have two water tanks, suspended with their water levels at equal heights above ground and you connect them, no water will flow because the gravitational potentials are the same. Same with a battery connected to a point with the same potential - no charge will flow.esha said:but if the batteries are present what prevents them from supplying current?