Page 51 - Physics_Form_2

Current electricity

Equivalent resistors
Depending on the purpose, fixed resistors where R is the total resistance, thus,
T
can be connected in either a parallel V = IR
or a series configuration. The resultant T
resistance in the circuit is called total IR = IR + IR + IR
resistance, effective resistance, or T 1 2 3
FOR ONLINE READING ONLY
equivalent resistance. IR = T ( I R + 1 R + 2 R 3 )

Resistors in series R = T R + 1 R + 2 R 3

When two or more resistors are connected When resistors are connected in series, the
end to end consecutively, and the same total resistance in the circuit is the sum of
current flows through each resistor, the individual resistances. Therefore, for
such a connection is said to be a series n resistors connected in series, the total
connection. A single-loop circuit with resistance is given by,
series combination of resistors and a R = R + R + R ++ n
... R
2
T
3
1
battery, is shown in Figure 2.9.
Note that when resistors are identical,
V the total resistance is given by R = nR ,
T
where R is the resistance of an individual
resistor and n is the number of identical
resistors.
1 2 3
Resistors in parallel
R R R
1 2 3
Resistors are said to be in parallel
Figure 2.9: A circuit with resistors connected connection when two or more resistors
in series are placed side by side with their
corresponding ends joined together,
The current flowing in the circuit is the such that the same p.d is applied to each
same at all points. The sum of the potential resistor. Figure 2.10 shows a circuit with
difference across all the resistors equals parallel connection of resistors and a
the potential difference across the battery. battery.
V
Therefore,
I R
V = V + 1 V + 2 V 3 A I 1 1

From Ohm’s law, the current, I, in the I 2 R 2
circuit is given by, B
I R
3 3
V
I = Figure 2.10: A circuit with resistors
R T connected in parallel

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Physics Form 2 Final.indd 45 25/10/2025 10:25