State Kirchhoff’s first law.
A cell with internal resistance is connected to two resistors of resistances
and
as shown below.
The potential differences (p.d.s) across and
are
and
respectively. The terminal p.d. across the cell is
. The current in the circuit is
. Use Kirchhoff’s laws to show that the total resistance
of the external circuit is given by
The electromotive force (e.m.f.) of the cell in the figure above is . The values of
and
are
and
respectively. The terminal p.d. of the cell is
. Calculate the internal resistance
of the cell.
A resistor of resistance is added to the circuit above so that the circuit is as shown.
State and explain the effect, if any, of this change on:
the current in the cell
the terminal p.d. of the cell.