Experiment - 11 :- Practice on measurement of parameters in combinational electrical circuit by applying Ohm’s Law for different resistor values and voltage sources

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 :

1. Draw the circuit diagram as shown above.
2. Arrange the apparatus as per the circuit diagram.
3. Clean the ends of the connecting wires with sand paper and make them shiny.
4. 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).
5. Determine the zero error and least count of the ammeter and voltmeter and record them.
6. Adjust the rheostat to pass a low current.
7. Insert the key K and slide the rheostat contact to see whether the ammeter and voltmeter are showing deflections properly.
8. Adjust the rheostat to get a small deflection in ammeter and voltmeter.
9. Record the readings of the ammeter and voltmeter.
10. Take atleast six sets of readings by adjusting the rheostat gradually.
11. Plot a graph with V along x-axis and I along y-axis.
12. The graph will be a straight line which verifies Ohm's law.
13. 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: