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

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

**(A) APPARATUS REQUIRED**

- Ammeter
- Voltmeter
- Accumulator
- Key
- Rheostat
- Given resistance wires
- 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∝Vconversely

V

∝Ior, 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**

No. of observations | Ammeter Reading(I) | Voltmeter Reading (V) |

i) | 0 | 0 |

ii) | 2*0.05=0.1 | 4*0.05=0.2 |

iii) | 3*0.05=0.15 | 6*0.05=0.3 |

iv) | 4*0.05=0.2 | 8*0.05=0.4 |

v) | 5*0.05=0.25 | 10*0.05=0.5 |

vi) | 6*0.05=0.3 | 12*0.05=0.6 |

**(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**:-

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