SUBTOPIC 7.2 FLOW OF ELECTRIC CURRENT IN A SERIES CIRCUIT AND PARALLEL CIRCUIT

CHAPTER 7.2

FLOW OF ELECTRIC CURRENT
IN A SERIES CIRCUIT AND
PARALLEL CIRCUIT

Prepared by Cikgu Husrita

ELECTRIC CIRCUIT COMPONENTS WITH SYMBOLS

Electrical component Symbol

Switch

Dry cell

Bulb

Voltmeter

ELECTRIC CIRCUIT COMPONENTS WITH SYMBOLS

Electrical component Symbol
Galvanometer

Ammeter

Resistor

Resistance

TYPES OF ELECTRICAL CIRCUIT

SERIES CIRCUIT PARALLEL CIRCUIT

An electric circuit is a complete passage that allows the current to
flow through it

SERIES CIRCUIT Current that flows through each bulb is the same

I = I₂ = I₃

Voltage that goes across the batteries is a total amount of the
voltage that goes across each bulb

V = V₁ + V₂

Effective resistance is the total resistance across the components

R = R₁ + R₂

All the components in the circuit receive the same amount of
current.

When the dry cells are increased, the brightness of the bulbs
increase

If one electrical component is damaged, the rest are unable to
function

Connecting more electrical component increases the resistance
and decreases the current

ANALYSING CURRENT, VOLTAGE AND RESISTANCE IN A SERIES
CIRCUIT

• In the series circuit, the current, voltage and resistance are inter-related.
• Advantages of series circuit
i. The current that flows through each of the electrical components is the same,

regardless of the size of its resistance
ii. Less wire is needed to set up series circuit

• Disadvantages of series circuit
i. If one of the bulb fuses, the rest will not light up
ii. When more bulbs are connected in series, the brightness of the bulbs decrease
iii. Each electrical component in the circuit cannot be switched off separately

PARALLEL CIRCUIT Current that flows through the circuit is the total amount of the current that
flows through each bulb
When more electrical components are
connected, the faster the dry cells become I = I₂ + I₃
weak.
Voltage that goes across each bulb is the same as the voltage that goes
across the batteries

V = V₁ = V₂

Effective resistance is calculated using the following formula:

11 1
R = R₁ + R₂

Increasing the number of electrical components does not jeopardies other
electrical equipment in the circuit.

If one electrical component is damaged, the rest of the components can still
function

The voltage of each electrical component cannot be controlled because the
voltage is the same as the source of voltage

ANALYSING CURRENT, VOLTAGE AND RESISTANCE IN A PARALLEL
CIRCUIT

• In the parallel circuit, the current, voltage and resistance are inter-related.
• Advantages of parallel circuit
i. Electrical components can be controlled by difference switches
ii. If one the bulbs blows out, the rest can still light up
iii. When more bulbs are connected in parallel, the brightness of the bulb do not

decrease

• Disadvantages of parallel circuit
i. Much more wire is needed to set up parallel circuit
ii. The set up of parallel circuits are more complex

Similarities
 voltage across the circuit is the voltage of the battery
 in both types of circuits, current flows form the positive

terminals to the negative terminals

Differences

Series circuit Parallel circuit

The current at any point in the circuit is the The total current is equal to the current in
same; the branches added together;

I = I1 = I2 I = I1+ I2 + I .....

The total voltage is equal to the voltages The voltage across each resistor is the same
across each resistor added together ; as the mains voltage;

V = V1 + V2 + ..... V = V1 = V2 = ......

The total resistance is equal to the The total resistance in the circuit is
resistance of the resistors added together: calculated from the formula:

R = R1 + R2 + ..... 1 = 1 + 1 + ………
R R1 R2