Ohm's law
What is Ohm's law ?
It is a law stated by
German physicist George
Simon ohm. It states that the electric
current flowing through a metallic wire
is directly proportional to the
potential difference across its ends
here is a metallic wire to verify the
Ohm's law we need to measure two things
1. the current flow through this wire
and the second is the potential
difference between the two ends.
How do we do that ?
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coming back to our lesson
To verify the Ohm's law, we
need a few cells, a cell holder,
a conductor, an ammeter to measure the
electric current and an voltmeter to
measure the potential difference. Now
connect the circuit and place only one
cell in the cell holder.
Let us note down readings in the ammeter and voltmeter
Put them in a table now we will add one
more cell to the circuit and note down the
readings once again. Take readings with
three cells and four cells also.
Now let us observe the table
plot these values on a graph having
current flow on x-axis and potential
difference on y-axis with one cell
current 0.15 and voltage 0.3 with two
cells the current 0.25 and voltage 0.5
with 3 cells 0.375 and 0.75
four cells 0.5 and 1.0
so we have plotted these values on the graph now the v-i graph has a straight line passing
through the origin which indicates that
v proportional to i or v/i is constant.
What is that constant ?
That is " r" the resistance.
so v/i is equal to r or v = ir
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