Verify ohm' law with the help of an activity
Answers
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:

As performed in the simulator:
Click on Show Label checkbox to label/unlable the apparatus in the circuit.Click on Show Help checkbox to show/hide the 'help' for performing the lab.Click on the Observation Table tab below to open the Observation table.Drag the plug key to switch on/off the current.Adjust the rheostat such that ammeter shows the low value of Current (I). Note corresponding voltmeter reading.Increase the current 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 and record in the Observation Table.Note V/I ratio for each set of reading in the Resistance column.Click on Plot Graph button to plot voltmeter readings (V) along the x-axis and the corresponding ammeter readings (I) along the y-axis in the graph.
Ohm s law:
The current through a conductor element is proportional to the potential difference applied between its ends provided the temperature remains constant.
Aim : To show that the ratio of V/I is a constant for a conductor.
Materials required : 5 dry cells of 1.5 V each, conducting wires, an ammeter, a voltmeter, thin iron spoke of length 10 cm, LED and key.
Procedure :
i) Connect a circuit as shown in the figure.
ii) Solder the conducting wires to the ends of the iron spoke and close the key.
iii) Note the reading of ammeter (current) and voltmeter (potential difference) and tabulate them.
iv) Now connect two cells in the circuit and note the respective readings of ammeter and voltmeter in the above table.
v) Repeat the above procedure using three cells, four cells and five cells respectively.
vi) Record the values of potential difference and current© corresponding to each case in the table.
vii) Find V/I for each set of values.
viii) We notice that V/I is constant.
ix) From this we can conclude that potential difference between the ends of the iron spoke is directly proportional to the current passing through it. This is ohm’s law.