Page 88 - Physics_Form_2

Physics for Secondary Schools

Arrangement of cells in series and The sum of individual internal resistances,
parallel r equals total internal resistance, r . If
T
Cells are often used in combination. A the four cells in Figure 2.56 are identical
battery is formed when two or more cells and have the same e.m.f and internal
are connected. Cells can be connected in resistance, then,
either series or parallel. r = T r + 1 r + 2 r + 3 r 4

Cells in series r = 1 Ω + 1 Ω +1 Ω + 1Ω = 4 Ω
T
To obtain a larger e.m.f, cells are arranged
in series as shown in Figure 2.56. The where r = 1 r = 2 r = 3 r 4
current flowing through the cells is the In the case of n cells:
same. The total voltage E across the nr
T
cells is equal to the sum of the voltage of r =
T
the individual cells. This is: Cells in parallel
E = T E + 1 E + 2 E + 3 E 4 Suppose four identical cells, each of
e.m.f. 1.5 V and internal resistance 1 Ω,
The total voltage, E for cell arrangements are arranged in parallel as shown in Figure
T
in Figure 2.56 is; 2.57. The total e.m.f. recorded when a
voltmeter is connected to terminals P and
6 V
1.5 V +
1.5 V +
1.5 V =
E = FOR ONLINE READING ONLY
1.5 V +
T
In the case of n cells, each of volts Q is the e.m.f of one of the four cells.
This is because the four cells operate
, E E = nE . together as a single cell whose component
T
6 V materials are the sum of those in the
individual cells. This is because the e.m.f.
of a cell is determined by the nature of the
chemicals used and not by their amount.
1.5 V 1.5 V
1.5 V 1.5 V
As a result, the e.m.f. equals that of one
(a) Cells in parrallel arrangement of the cells.
Cell 1 Cell 2 Cell 3 Cell 4

1.5 V 1.5 V 1.5 V 1.5 V 1.5 V
(b) Cells in circuit diagram 1.5 V 1.5 V 1.5 V 1.5 V

Figure 2.56: Cells in series
If cell 3 is reversed in Figure 2.56, then (a) Cells in parrallel arrangement
the equivalent e.m.f. is given by,
E = T E + 1 E + 2 E + 3 E 4

E  T 1.5 V  1.5 V  1.5 V  1.5 V  4.5 V (b) Cells in circuit diagram

Therefore, E = 4.5 V . Figure 2.57: Cells in parallel
T

82
Student’s Book Form One

Physics Form 2 Final.indd 82 25/10/2025 10:26