FORM 2 CHAPTER 7 ELECTRICITY AND MAGNETISM

• the rubber of the belt will become
negatively charged while

• the acrylic glass (dome) of the upper
roller will become positively charged.

• The belt carries away negative charge on
its inner surface while the upper roller
accumulates positive charge.

• The deflection of the galvanometer’s pointer
indicates the flow of the electric current.

Electric current

• Electricity is the flow of electrical charges
(electrons) in one direction.

• The continuous flow of electrons form an
ELECTRIC CURRENT.

ELECTRIC CURRENT/
ELECTRICITY

• Energy is needed for electrons (electric

charges) to flow continuosly.

• Sources of energy:
Dry cells (batteries)
Solar cells
Electrical generators

Electric current, voltage and resistance.

Terms Meaning

Voltage (V): The energy needed to move the
electrical charges from one point to
another.

Electric current (I) the continuous flow of electrons in an
electric circuit.

resistance (R) the property of resisting or opposing
the flow of electrical charges through it.



Connection of ammeter (series)

An ammeter is connected in series to the electric circuit.



Connection of voltmeter (parallel)

A voltmeter is connected in parallel to the
electric circuit.





Ohm’s Law

• Ohm’s Laws states that the current (I) flowing
through a conductor is directly proportional
to its voltage (V).

V = IR





7.2 flow of electric current in a series
circuit and parallel circuit.

• Electric current requires a complete path
to flow known as electric circuit.

• Made up with different electrical component.
(pg153)

7.2 flow of electric current in a series
circuit and parallel circuit.

• 2 types of circuit:
-series circuit
-parallel circuit.

7.2 flow of electric current in a series
circuit and parallel circuit.

• 2 types of circuit:

1) series circuit

Electrical components that are connected one
after another where the current flows through a
single path.

7.2 flow of electric current in a series
circuit and parallel circuit.

• 2 types of circuit:

2) Parallel circuit

A circuit that is separated into several
different paths and each path has electrical
components.



Circuit diagrams

• Closed circuit – The switch is closed and there is no gap in the
circuit. Electric current can flow from one end of the dry cell to
the other and the bulb will light up.

• Open circuit – the switch is open, therefore, there is a gap in the
circuit. Electric current cannot flow in the circuit and the bulb will
not light up.

7.5: PARALLEL AND SERIES CIRCUIT

• Series circuit parallel circuit

Parallel circuit

Series circuit



Numerical problem

• Example 1
In circuit P, if the current passing through one
bulb is 2A and the voltage across the bulb is 8V,
what is the resistance of the bulb?

Textbook page 157…

7.8 MAGNETISM

1. The characteristics of a magnet are:
(a) A magnet has two poles – the north and the south poles.
(b) The same poles repel, different poles attract each other.
(c) A free hanging magnet always points in the north-south

direction.
(d) A magnet can attract iron, steel, cobalt and nickel.
2. A magnetic field is a field of force surrounding a magnetic
body.

• Magnetic filed: the area around the magnet
with magnetic force.

• Neutral point: space that does not have any
magnetic field.



The characteristics of magnetic field lines

1. The magnetic field lines begin from the north
pole and end at the south pole.
2. The magnetic filed lines are closer to one
another where the magnetic filed is stronger.
3. The magnetic field lines never meet or across.



MAGNETIC FIELD LINES

Electromagnet

1. An electromagnet is a type of magnet that has
temporary magnetic effect when electric current
flow through it.



• The magnetic field lines around a wire carrying
an electric current are circular.

• They form concentric circles with the wire as
the centre and are further apart as they get
further from the wire.

• The direction of the
magnetic field depends on
the direction of the
current flowing in the
wire.

• It can be determined by
using a simple method
called ‘ right – hand grip
rule’.

Application of magnets and
electromagnets in daily life

• Telephone
• Electric bell