Explanation
Battery is short circuited so potential difference is zero.
To verify Ohm’s law one galvanometer is used as ammeter and other galvanometer is used as voltmeter. Voltmeter should have high resistance and ammeter should have low resistance as voltmeter is used in parallel and ammeter in series that is in option (c).
For portion CD slope of the curve is negative i.e., resistance is negative.
When we move in the direction of [he current in a uniform conductor, the potential difference decreases linearly. When we pass through the cell, from it’s negative to it’s positive terminal, the potential increases by an amount equal to it’s potential difference. This is less than it’s e.m.f, as there is some potential drop across it’s internal resistance when the cell is driving current.
At point A the slope of the graph will be negative. Hence resistance is negative.
To make range n times, the galvanometer resistance should be G/n, where G is initial resistance.
Resistance of metallic wire increase with rise of temperature.
As the magnetic field is greater, the critical temperature is lower and as B2 is larger then B1. Graph (a)is correct.
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