Question

State Ohm’s law and draw a neat labelled circuit diagram containing a battery, a key, a voltmeter, an ammeter, a rheostat and an unknown resistance to verify it. 

Answer 1

It states that electric current flowing through a metallic wire is directly proportional to the potential difference V across its ends provided its temperature remains the same. This is called Ohm's law.
V = IR

Experimental Verification: Reassemble the circuit according to the diagram. The circuit consists of a battery, an unknown resistance, a voltmeter with its positive terminal facing the battery's anode, and a rheostat and ammeter connected in series. With the key closed, and the rheostat set to zero, the ammeter and voltmeter should display the lowest possible readings. After that, the rheostat is adjusted step-by-step, and the values of A and V are recorded at each interval. The ratio of `"V"/"I"` is always found to be constant. This verifies Ohm's Law.

The temperature and other physical parameters of the conductor must be kept constant.