Define Potential difference(P.d) of cell and state relation between emf and P.d of cell.
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Answer:
The potential difference across the two points of a conductor causes the dissipation of electrical energy into other forms of energy as charges flow through the circuit.
When one end A of a conductor is connected to the positive terminal and its other end B is connected to the negative terminal of the battery, then the potential at A becomes higher than the potential at the B.
This causes a potential difference between the two points of the conductor.
Relation between them:- Their relation is V=E-Ir. But while charging of secondary cell It become V=E+It.Why is there a change
Their relation is V=E-Ir. But while charging of secondary cell It become V=E+It.Why is there a change in sign of
V is the potential difference across the terminals of the cell and E is the emf of the cell.
The emf is set up by an electrochemical process within the cell.
The potential difference across the internal resistance of the cell is always Ir with the current flowing from the node at the higher potential to the node at the lower potential.
V=E−Ir
In the top diagram the current I is flowing from left to right so the potential of node B is greater than that at node C by Ir.
Starting at node A and going through the cell to node B results in an increase of potential of E and then going through the resistor from node B to node C there is a decrease in potential of Ir.
So node C is higher in potential than node A and the potential difference is E−Ir=V.
In this instance the cell is a source of electrical energy.
V=E+Ir
In the lower diagram the current is flowing from right to left with the potential of node C′ higher than that of node B′ by Ir
Starting at node A′ and going through the cell to node B′ results in an increase of potential of E and then going through the resistor from node B′ to node C′ there is an increase in potential of Ir.
So node C′ is higher in potential than node A′ and the potential difference is E+Ir=V.
In this instance the cell is a sink of electrical energy.