Potentiometer Video Lecture | Physics for ACT

potentiometer a potentiometer as the
name suggests is an instrument to use to
measure an unknown potential difference
the potentiometer has for 1 meter long
wires stretched battle to each other on
a broad wooden board by the side of a
metre scale pass wire is generally made
of Eureka or manganese and is stretched
along a wooden board with its ends fixed
to thick copper strips the end a reads
zero centimeter and the length of the
wire between a and B is 400 centimeters
the wire is connected to a source of
constant EMF through a rheostat an
ammeter and a one-way key K a
galvanometer is connected between the
end a of the wire and the jockey or
slider s
principal when a current flows through a
wire of uniform thickness and same
composition potential difference between
its two points is statically
proportional to the length of the wire
between the two points we is directly
proportional to L or we is equal to K L
where K is the constant of
proportionality call the potential
gradient a potentiometer works on this
principle if we plot a graph between we
and L a straight line graph is obtained
you
comparison of EMF of two cells a
potentiometer can be used to compare the
EMFs of two cells for comparing the EMFs
of two cells arrange the cell as shown
the EMF of the driving battery is
constant and more than that of given
experimental cells u1 empty to the
positive terminal of the cells II 1 and
E 2 are connected to the zero in
Terminal A of the potentiometer there as
the negative terminals are connected
through a two wiki to a galvanometer and
a jockey the measurement of EMF is
carried out in two steps
close the main key K and the key k1 so
that the semi one comes into circuit
the joking is moved gently along the
potentiometer wire a-b till a point is
obtained where the galvanometer shows no
deflection let the spawn J be at a
distance L one from the zero end at this
point E one is directly proportional to
the length of the balancing wire a 1 is
equal to K into L 1 where K is the
constant of proportionality click on the
keys K and K 1 to open the circuit
now close the main key K and the key k2
so that the cell e2 comes into circuit
the jockey is again moved along the
potentiometer to find the balancing
point let this point be at a distance L
- from the zero end at this point E - is
directly proportional to the length of
the balancing wire e 2 is equal to K L
to the EMFs are compared by dividing the
two equations a 1 is equal to K L 1 and
E 2 is equal to K L - that is e1 by e2
is equal to L 1 by L 2 if one of the
cells is a standard cell the EMF of the
other cell can be found accurately
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