Question

nd the current
112. That is,
Figure 12.2 Electric circuit for studying Ohm's law
it. Its SI
's law,
yough
Ohm
R=0
if the potent
к
Pirst 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 Vand current I.
Also from
I=V/RO
It is obvic
persely pro
rent gets
decrease
regulate cu
resistance.
pchanget
resistance
V/I
(volt/ampere)
Acti
Potential difference
S.
Current through
Number of cells
No. used in the
across the
the nichrome
nichrome
circuit
wire, I
(ampere)
wire, V (volt)
OISA
1
2
2
1A
3
3
3
uisu
list
8A
Plot a graph between V and I, and observe the nature of the graph.
Tak
key
is
Set
lea
In this Activity
you will find that​

Answer 1

(a)The potential difference across the ends of a given metallic wire in an electric circuit is directly proportional to the current flowing through it, provided its temperature remains the same. This is called Ohm’s law.

(b) Experiment to verify Ohm's law:

Set up a circuit as shown in figure shown, consisting of a nichrome wire XY of length, say 0.5m, an ammeter, a voltmeter and four cells of 1.5V each. 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 a table. 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. In this experiment, we will find that approximately the same value for

I

V

is obtained in each case. Thus the V–I graph is a straight line that passes through the origin of the graph, as shown in the figure. Thus, V/I is a constant ratio, which verifies Ohm's law.