Verification of Ohm's Law

Procedure to perform the experiment in OLABS  :

  1. Drag the plug key to switch on or off the current,  and adjust the rheostat to pass a small current through the given resistor. Note the ammeter and voltmeter readings.

  2. Increase the current step-by-step by adjusting the slider of the rheostat and take about 5 or 6 sets of readings. Note carefully ammeter and voltmeter readings in each set.

  3. Tabulate the observations as given in the observation table.

  4. Find V/I ratio  in each of observations and record it in the observation table.

  5. Open the graph.

  6. Draw a graph by plotting voltmeter readings(V)  along the X-axis and the corresponding along the ammeter readings(I) Y-axis as shown in the diagram below.

          

Procedure to perform the experiment in physical laboratories :

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 :

  1. Range
    Range of the given Ammeter = ..................... A
    Range of the given voltmeter = .....................V

  2. Least Count
    Least Count of the given Ammeter = ..................... A
    Least Count of the given voltmeter = .....................V

  3. Zero Error
    Zero Error of the given Ammeter = ..................... A
    Zero Error of the given voltmeter = .....................V

  4. Zero Correction
    Zero Correction of the given Ammeter = ..................... A
    Zero Correction of the given voltmeter = .....................V

  5. Note the readings as mentioned above in the obvervation table.

Calculations :

  • Mean Value of V/I from observations, R = .......... Ω.

  • Slope of I vs V graph = ...........

  • R from graph = 1/ slope = .............. Ω.

 

Result :

  • Ohm's Law is verified as the I vs V graph is a straight line.

  • The resistance of the given wire = ................... Ω.

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