Material required :
A resistor of about 5 Ω, an ammeter ( 0 - 3 A), a voltmeter (0 - 10 V), four dry cells of 1.5 V each with a cell holder (or a battery eliminator), a plug key, connecting wires, and a piece of sand paper.
Precautions :
- All the electrical connections must be neat and tight.
- Voltmeter and Ammeter must be of proper range.
- The key should be inserted only while taking readings.
Circuit Diagram:
Procedure :
- Draw the circuit diagram as shown above.
- Arrange the apparatus as per the circuit diagram.
- Clean the ends of the connecting wires with sand paper and make them shiny.
- Make the connections as per circuit diagram. All connections must be neat and tight. Take care to connect the ammeter and voltmeter with their correct polarity. (+ve to +ve and -ve to -ve).
- Determine the zero error and least count of the ammeter and voltmeter and record them.
- Adjust the rheostat to pass a low current.
- Insert the key K and slide the rheostat contact to see whether the ammeter and voltmeter are showing deflections properly.
- Adjust the rheostat to get a small deflection in ammeter and voltmeter.
- Record the readings of the ammeter and voltmeter.
- Take atleast six sets of readings by adjusting the rheostat gradually.
- Plot a graph with V along x-axis and I along y-axis.
- The graph will be a straight line which verifies Ohm's law.
- Determine the slope of the V-I graph. The reciprocal of the slope gives resistance of the wire.
Observations:
- Range of the given ammeter=.................... A.
- Least count of the given ammeter = ..................... A.
- Range of the given voltmeter = .....................V.
- Least count of the given voltmeter = .....................V.
- Mean value of V/I from observations, R = .......... Ω.
Observation from graph:
- Slope of I vs V graph = ...........
- R from graph = 1/ slope = .............. Ω.
Observation table:
