Activity 11.1

Activity . Set up a circuit as shown in Fig. . , consisting of a nichrome wire XY of length, say . m, an ammeter, a voltmeter and four cells of . V each. (Nichrome is an alloy of nickel, chromium, manganese, and iron metals.) First use only one cell as the source in the circuit. Note the reading in the ammeter I, for the current and reading of the voltmeter V for the potential difference across the nichrome wire XY in the circuit. Tabulate them in the Table given. Next connect two cells in the circuit and note the respective readings of the ammeter and voltmeter for the values of current through the nichrome wire and potential difference across the nichrome wire. Repeat the above steps using three cells and then four cells in the circuit separately. Calculate the ratio of V to I for each pair of potential difference V and current I . S. Number of cells Current through Potential difference V/I No. used in the the nichrome across the (volt/ampere) circuit wire, I nichrome (ampere) wire, V (volt) Plot a graph between V and I , and observe the nature of the graph. Electric bulb or A resistor of resistance R Variable resistance or rheostat or Ammeter Voltmeter Figure . Figure . Figure . Figure . Figure . Electric circuit for studying Ohm’s law Figure . Figure . Figure . Figure . Figure . V–I graph for a nichrome wire. A straight line plot shows that as the current through a wire increases, the potential difference across the wire increases linearly – this is Ohm’s law.