# How to verify OHM’s law using an Ammeter and Voltmeter

## To verify OHM’s law using an Ammeter and Voltmeter

OBJECT:- To verify OHM’s law using Ammeter and Voltmeter

(A) APPARATUS REQUIRED

1. Ammeter
2. Voltmeter
3. Accumulator
4. Key
5. Rheostat
6. Given resistance wires
7. Connecting wires

(B) THEORY:-

OHM’S Law states that at a constant temperature, the current flowing through any conductor is directly proportional to the potential difference at its ends.

i.e, I∝V

conversely

VI

or, V=IR——(1)

Where ‘R’ is proportionally constant known as the electrical resistance of the conductor.

The equation—(1) is identical to y=mx, which is an equation of a straight line passing through the origin with slope ‘m’. Hence, if we plot a graph ‘I’ and ‘V’ for a conductor wire, the result is a straight line passing through the origin. Then, ohm’s law is said to be verified. The slope of the straight line gives the value of resistance of the wire.

(C) OBSERVATION:-

Value of 10 divisions of voltmeter=0.5mv

or, the value of 1 division of voltmeter=0.05mv

Value of 10 division of ammeter=0.5mA

or, the value of 1 division of ammeter=0.05mA

OBSERVATION TABLE

(D) CONCLUSION:-

The value of V/I is found to be sensibly constant. Also, the graph of ‘V’ against ‘I’ is found to be a straight line passing the origin. Hence, ohm’s law is verified.

(E) PRECAUTIONS:-

1. Connecting wires should be of appropriate length i.e, too long wire is not preferable.
2. The length of the wire should be accurately measured.
3. High current should not be passed.
4. Reading should be taken carefully.
5. Sensitive instruments should be used.