2. 1 | P h y s i c
Theme1 General Physics
Measure Instrument
- Vernier calipers + micrometer screw gauge
Pendulum – one oscillation
√
***even in a vacuum, T of different l is not the same
Speed: the distance moved per unit time
Velocity: the change in displacement per unit time
Displacement: distance in a specific direction
Acceleration: the change in velocity with time
Addition formula
( )
Air resistance: a frictional force
1. Apply on only moving objects
2. Air resistance↑ when Speed↑ surface area↑ density of air↑
Force: a push or pull that one object exerts on another
Scalar: only magnitude

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Vector: direction + magnitude
***For an object with constant velocity or zero acceleration, the
resultant force/net force is zero
Newton’s 1
st
law
‚Every object will continue in its state of rest or uniform motion in a
straight line unless a resultant force acts on it to change its state‛
Newton’s 2
nd
law
‚When a resultant force acts on an object of constant mass, the object
will accelerate and move in the direction of the resultant force. The
product of the mass and acceleration of the object is equal to the
resultant force.‛
Newton’s 3
rd
law
‚For every action, there is an equal and opposite reaction, and these
forces act on mutually opposite bodies.‛
Mass: a measure of the amount of matter or substance in a body
Weight: a force due to gravity
Gravitational field: the region surrounding the Earth where gravity is
experienced
Gravitational field strength: the gravitational force acting per unit
mass on an object
Inertia: the reluctance of the object to change its state of rest or
motion
***Inertia depends on only the mass of the object
Density: mass per unit volume

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Moment: the product of the force and the perpendicular distance from the
pivot to the line of action of the force
***Taking moments to the pivot, sum of anti-clockwise moment = sum of
clockwise moment
Principle of Moments
‚When a body is in equilibrium, the sum of clockwise moment about a
pivot is equal to the sum of anti-clockwise moment of the same pivot‛
Centre of Gravity: the point through which its whole weight appears to
act for any orientation of the object
*** A plumb line is used to find CG
Stability: the ability of an object to return to its original object
after it has been tiled slightly
Stable, Unstable and Neutral equilibrium (CG remains at the same level
when it is tiled slightly)
***Low CG and wide base to increase stability
Energy: the capacity to do work
Kinetic Energy: the energy possessed by a body due to its virtual of
motion
Gravitational Potential Energy: the energy possessed by a body due to
virtual of its position
Principle of Conservation of Energy
‚Energy can neither be created nor destroyed in any process. It can be
converted from one form to another or transferred from one body to
another, but the total amount remains constant‛

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Work: the product of the force and the distance moved by the object in
the direction of the force
(1J=1Nm)
Power: the rate of woke done
(1W=1J/s)
Pressure: the force acting per unit area
,
*** Barometer is used to measure the atmospheric pressure
Theme2 Thermal Physics
Temperature: how hot or cold an object is
Heat: the amount of energy that is being transferred from a hotter to a
colder region
Thermocouple – electromotive force ( )
Factors affecting range, sensitivity and responsiveness

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State Arrangement Movement
s
Closely packed in a regular
pattern
Vibrate about their fixed
position
l
Closely packed in a disorderly
manner
Sliding over each other
g
spread far apart in a disorderly
manner
Move rapidly at random
Brownian motion: the random, continuous and uneven movement of particles
suspended in a fluid
Boyle’s Law: pressure is inversely related to volume when the other
factors are constant
Overall formula
Key concepts
When the container is heated up (temperature increases); the particles
gain more kinetic energy and move faster randomly, the rate of collision
between the particles and the inner wall is more frequent, the total
force exerted to the inner wall increases, the pressure increases
When the volume is decreased; the space between the particles is
smaller, the number of molecules presented per unit volume increases,
the rate of collision between the particles and the inner wall
increases, the total force exerted to the inner wall increases, the
pressure increases

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Conduction: the process of thermal energy transfer without any flow of
the material medium
- Particle vibration; metal and non-metal
- Free electron diffusion; only metal
Convection: the transfer of thermal energy by mean of currents in a
fluid
Radiation: the continual emission of infrared waves from the surface of
all bodies, transmitted without the aid of a medium
***Dull, black surfaces are better emitters of infrared radiation than
shiny, white surfaces
Internal energy: The total kinetic and potential energy associated with
the motions and relative positions of the molecules of an object
Heat capacity(C): the amount of thermal energy required to raise the
temperature of a body by 1K (or 1˚C)
Specific heat capacity(c): the amount of thermal energy required to
raise the temperature of 1kg of a substance by 1K (or 1˚C)
Melting: the process of the change of solid state to liquid state
P b.p.
***increase pressure increase the melting point of water
Latent heat: the energy released or absorbed during a change of state
Latent heat of fusion: the amount of thermal energy required to change a
body from solid to liquid state, or vice versa, without a change in
temperature
Specific latent heat of fusion: the amount of thermal energy required to
change 1 kg of solid to liquid, or vice versa, without a change in
temperature

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Latent heat of vaporisation: the amount of thermal energy required to
change a body from liquid to vapour, or vice versa, without a change in
temperature
Specific latent heat of vaporisation: the amount of thermal energy
required to change 1 kg of liquid to vapour state, or vice versa,
without a change in temperature
,
Boiling: the process of the change of liquid state to gaseous state at a
fixed and constant temperature
Boiling Evaporation
1. Occurs at a fixed temperature 1. Occurs at any temperature
2. Quick process 2. Slow process
3. Takes place throughout the
liquid
3. Takes place only at the liquid
surface
4. Bubbles are formed in the liquid
4. No bubbles are formed in the
liquid
5. Thermal energy supplied by an
energy source
5. Thermal energy supplied by the
surroundings
Theme3 Light, Waves and Sound
Luminous and non-luminous object
Number of imaged formed – always round down
Refraction: Bending effect of light as it passes from one optical
material to another
Refractive index – Snell’s Law

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***light travels from lesser density to higher density
Critical angle: the angle of incidence in the optically denser medium
for which the angle of refraction in the less dense medium is 90°
Total internal reflection takes place only when
1. A ray of light travels from an optically denser to a less dense
medium
2. The angle of incidence in the optically denser medium is greater than
the critical angle
Optical fibres
_ can carry a much higher volume of information over long distances than
the electrical wires
_ lighter, thinner and cheaper for manufacture
_ high quality transmission of information over long distances with
negligible loss
Laws of Reflection1
1. Angle of incidence is equal to the angle of reflection
2. The incident ray, reflected ray and the normal at the point of
incidence all lie on the same plane
Lens
Periodic motion: motion repeated at regular intervals
***the source of any wave is a vibration or oscillation
***waves move/propagate through the medium
***In waves, energy is transferred without the medium being transferred

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Types of wave motion
1. Longitudinal waves: waves that travel in a direction parallel to the
direction of the vibration
2. Transverse waves: waves that travel in a direction perpendicular to
the direction of the vibration
Crests: the highest points of a transverse wave
Troughs: the lowest points of a transverse wave
***Compressions & rarefactions in longitudinal waves
Phase: any two points that move in the same direction, have the same
speed and same displacement from the rest position
Wavelength (λ): the shortest between two points that are in phase
Amplitude (A): the maximum displacement from the rest
Period (T): the time taken for one point on the wave to complete one
oscillation
Frequency (ƒ): the number of complete waves produced per second
ƒ
Wave speed (v)

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λ
ƒλ
Wave front: an imaginary line on a wave that joins all points that are
in the same phase
Refraction of waves
*** v & λ decrease from deep to shallow water
Reflection of waves
- i = r
- f, λ, v are the same
Electromagnetic waves – low f, high λ to high f, low λ
; Radio waves  microwaves  infrared  visible light*  ultraviolet
 X-rays  gamma rays
***red  blue
Properties of Electromagnetic waves
1. They are transverse waves. They are electric (horizontal) and
magnetic (vertical) fields that oscillate at 90 to each other
2. They transfer energy from one place to another

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3. They can travel through vacuum, do not require any medium
4. Their speed in vacuum is 3.010
8
m/s
2
5. ƒλ
6. They obey the laws of reflection and refraction
7. They carry no electric charge
8. Their ƒ do not change when travel from one medium to another. Their ƒ
depend only on the source of the wave. Their v and λ change.
Ionisation: the process of ion formation
Ionising radiation: the rejection of one or more electrons from an atom
or molecule to produce a fragment with a net positive charge
Effects of ionising radiation
1. Molecular level: irradiation of human tissues, damage to proteins,
nucleic acid
2. Sub-cellular level: damage Chromosomes (DNA)
3. A pregnant woman: an abnormal pattern of cell division, leading to
cancers such as leukaemia
4. Organism level: premature aging and shortening of lifespan
***Sound is longitudinal wave
***Sound is produced by vibrating sources placed in a medium
***the series of compressions and rarefactions produced by the shifting
of air layers
Compressions – slightly higher pressure than the surrounding air
pressure
Rarefactions – slightly lower pressure than the surrounding air
pressure

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Wavelength of the sound (λ): the distance between two consecutive
compressions or rarefactions
Amplitude of the sound (A): the maximum pressure change
Medium of transmission of sound
V gas  5 =V liquid
V gas  15 =V solid
V solid > V liquid > V gas
√ , T=temperature
Reflection of sound
Echo: the repetition of the clap
***an echo is formed when a sound is reflected off hard, flat surfaces
Range of audibility: the range of frequencies which a person can hear
***human ears – 20 Hz-20,000 Hz
Ultrasound: sound with frequencies above the upper limit of the human
range of audibility (above 20,000 Hz)
Infrasound: sound with frequencies below the lower limit of the human
range of audibility (above 20 Hz)
Pitch – a music note or sound as ‘high’ or ‘low’
ƒ
Loudness: the volume of a sound related to the amplitude of a sound
Theme4 Electricity and Magnetism

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Electrostatics: the study of static electric charges
***same charges – repel (repulsive force)
***different charges – attract (attractive force)
The amount of charge an e-
/P+
has is 1.610-19
C
6.2510
-19
electrons = 1 C
Electrical insulators: materials where electrons are not free to move
about
***they are charged by friction
Electrical conductors: materials that allow electrons to move freely
within them
***they are charged by induction
Induction: the process of charging a conductor without any contact with
the charging body
Induction – 2 metals
1. Two conductors (metal spheres) on insulating stands are placed
touching each other
2. A negative charged rod is brought near sphere A. This causes the
electrons in the metal spheres to be replied to the far end of sphere B.
Sphere A can be seen to have excess positive charges, while sphere B has
excess positive charges.
3. Without removing the rod, separate spheres A and B.
4. Remove the charged rod. Spheres A and B now have equal amounts of
opposite charges. Spheres A and B have been charged by induction.
Induction – 1 metal

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1. Bring a positively charged glass rod near the metal conductor on an
insulating stand. The free electrons in the metal will be drawn towards
the side nearer the positively charged glass rod.
2. Without removing the glass rod, earth the positively charged side of
the metal conductor by touching in with your hand. The human body is a
relatively good conductor and will allow electrons to flow into the
conductor from the ground. This will neutralize the positive on this
side of the conductor.
3. With the glass rod still in place, remove your hand from the
conductor. This will stop the earthing process.
4. Remove the glass rod. The negative charges will be redistributed on
the surface of the conductor. The conductor is now negatively charged.
Electric force: a force experienced by charges
An electric field: a region where an electric charge experiences an
electric force
Electric lines of force: imaginary lines, showing the path a positive
charge would take if it was free to move.
The direction of the field: the direction of the force on a small
positive charge
***The strength of an electric field is indicated by how close the filed
lines are to each other

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An electric current is caused by a flow of electrons
Electron flow: movement of electrons from the negatively charged end to
the positively charged end
Convectional current flow: the assumption that an electric current
consist of positive charges flowing from the positively charged end to
the negatively charged end
An electric current (I): a measure of the rate of flow of electric
charge (Q) through a given cross section of a conductor
An electric circuit: a complete or close path through which charge can
flow from one terminal of an electrical source to the other terminal
The electromotive force (e.m.f.) of an electrical energy source: the
work done by the source in driving a unit charge round a complete
circuit
Cells in series
‚The combined e.m.f. in increased because electric charges gain
electrical energy from each cell when they pass through them.‛
Cells in parallel

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‚The energy required to move electric charges through the load will be
contributed equally by each cell. Thus, each cell only needs to provide
half the energy to move the charges through the circuit.‛
Potential difference (p.d.) between two points in an electric circuit:
the amount of electrical energy converted to other forms of energy when
one coulomb of positive charge passes between the two points
Resistance: a property of the material that restricts the movement of
free electrons in the material
The resistance (R) of a component: the ratio of the potential difference
(V) across it to the current (I) flowing through it
A resistor: a conductor in a circuit that has a known value of
resistance
Ohm’s Law
‚The current passing through a metallic conductor is directly
proportional to the potential difference across its ends, provided the
physical conditions are constant‛
***ohmic conductors – conductors that obey Ohm’s Law
*** I-V graph: a straight line passes through the origin
Non-ohmic conductors – I-V graph is not a straight line ( is not a
constant)
Ex; Filament lamp, thermistor, semiconductor diode

18. 17 | P h y s i c
Resistivity (ρ)
Series Circuits
‚When similar resistors are connected in series, the combined
resistance is larger than the individual resistance of a single
resistor. As a result, this cause the current in the circuit to be
smaller if the e.m.f. supplied in the same.‛
‚In a series circuit, the sum of the potential across each component is
equal to the difference across the whole circuit‛
‚The combined resistance of resistors in series is the sum of all the
resistances.‛
Parallel Circuits

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‚In a parallel circuit, the sum of the individual currents in each of
the parallel branches is equal to the main current flowing into and out
of the parallel branches.‛
***Bulbs connected in parallel will glow more brightly than when
connected in series
***Another advantage of connecting bulbs in parallel is that when one of
the light bulbs blows, the other light bulb will continue to glow –
there is still a complete circuit through the other parallel branch for
the current to flow
≠
***When one of the bulbs in series blows, the entire circuit will be
open and the other bulb will not light up
Potential Divider: A circuit with resistors arranged in series
( )

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Transducers: electric or electronic devices that convert energy from one
form to another – they respond to physical quantities such as
temperature and light
Input transducers – convert non-electrical energy to electrical energy
Output transducers – convert electrical energy to non-electrical energy
Ex; Thermistors, Light-dependent resistor (LDR)
Thermistors –
Light-dependent resistor (LDR) –
Electric heating
_ Usually made up of nichrome wire; because of its high resistivity and
ability to withstand high temperature;
_ As it has high resistivity, the electric current is decreased and
hence the temperature cannot reach the m.p. and b.p.
_ Thermal energy is generated when an electric current passes through
the heating element

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Electric lighting – filament & fluorescent lamp
Filament lamp
_ Filament is made of a tungsten coil; tungsten has high resistivity and
m.p. (3400°C)
_ Filament is thin (small cross-sectional area – A)
***↑ρ ↑l ↓A  ↑R  ↓I  temperature cannot reach the m.p.
_ contains Argon and Nitrogen to prevent the tungsten to burnt
Fluorescent lamp
_ more efficient than filament lamps (3000 hours vs 1000 hours)
_ use less energy than filament lamps
_ light produced when passing electric charges between two electrodes
_the mercury vapour contained in the glass tube emits ultraviolet light
with invisible light which is converted to visible light by fluorescent
powder coated on the inner wall
Advantages Disadvantages
Filament
Give cosy and relaxed
atmoshere
10%  light
90%  heat
Fluorescent Energy efficient Costly & toxic
Electric motors
_ work on the principles of the magnetic effects of a current
_ electric energy  rotational kinetic energy
Power: the rate of woke done or energy converted
Dangers of Electricity
Damage insulation
_ electrical insulation crack and break; exposing the conducting wires
inside
_ cause severe electric shock if it is touched
Overheating of cables
_ an unusually large current flows through the conducting wires

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_ the higher resistance of thinner wires will produce more thermal heat
that will damage the insulation and may cause a fire
***thin wires are used for appliances that need less power and vice
versa
Damp conditions
_ as our human body can only withstand a current of about 50mA, the
large current will electrocute the person
_ R of human body is low; ↓R  ↑I ***
Safe use of electricity at home
_ electricity is supplied by a cable containing 2 wires – live wire (L)
and neutral wire (N)
live wire (L) – 240V
neutral wire (N) – 0V
These 2 wires are connected to a main fuse box, an electricity meter and
a consumer unit.
The consumer unit: the distribution point for the household’s
electricity supply. – consists of a main switch and circuit breakers
1. Circuit breakers: safety devices that can switch off the electrical
supply in a circuit when there is an overflow of current
1.1 Miniature Circuit Breaker (MCB): when the current exceeds the
current values labeled, the circuit breaker will trip.
1.2 Earth Leakage Circuit Breaker (ELCB): detects the small current
leakages from the live wire to the earth wire. When this happens, the
current in the live wire will be greater than the neutral wire, causing
the ELCB to trip.
2. Fuses: safety devices included in an electrical circuit to prevent
excessive current flow
_ same function as the MCB

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_ A fuse consists of a short thin piece of wire which becomes hot and
melts when the current flowing through it is greater than its rated
value.
a. Fuses should have a current rating just slightly higher than the
current an electrical appliance will use under normal
b. A fuse should be connected to the live wire so that the appliance
will not become charged after the fuse has melted due to the over flow
of current
c. Before you charge a fuse, always switch off the mains power supply
3. Switches
_ they break or complete an electrical circuit
‚If the switch id fitted onto the neutral wire, the appliance will be
‘live’ even though the switch is ‘off’. Anybody who touches the
metal casing the appliance would experience an electric shock.‛ –
wrong
_ Switches must be fitted onto the live wire so that switching off dis
connects the high voltage from an appliance – correct
4. Plugs and sockets
_ a cartridge fuse protects the appliance from excessive current flow
5. Earthing
_ earth wire (E) – green & yellow
_ live wire (L) – brown
_ neutral wire (N) – blue

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The earth wire: a low-resistance wire which usually connected to the
metal casing of the appliance
‚If there is a fault – the live wire touches the metal casing of the
appliance – the user could get an electric shock.‛
_ the earth wire connected to the metal casing diverts the large current
due to the electrical fault to the ground
6. Double insulation
_ a safety feature which provides 2 levels of insulation in an
electrical appliance that can substitute the earth wire
6.1. The electric cable is insulated from the internal components of the
appliance
6.2. The internal components are also insulated from the external casing
Magnetite: a naturally occurring iron oxide mineral
Magnetic/ferromagnetic materials: the materials that are attracted by a
natural magnet
A permanent magnet: a material that retains its magnetism for a long
time
Properties of magnets
1. The poles are where the magnetic effects are the strongest.
2. When we suspend a bar magnet freely, the north-seeking pole will
point to the North Pole and the south-seeking pole will point to the
South Pole.
3. Law of magnetism
‚Like poles repel, unlike poles attract‛
Repulsion: the only test to confirm that an object is a magnet
Magnetic Induction: the process where ferromagnetic materials become
magnetised when they are near or in contact with a permanent magnet

25. 24 | P h y s i c
Theory of magnetism
‚If we take a bar magnet and cut it into three smaller pieces, we will
notice that every piece becomes a magnet itself with an N pole and an S
ploe.‛
A magnetic domain: a group of atomic magnets pointing in the same
direction
***In a permanent bar – the magnetic domains point in the same
direction
***In an unmagnetised bar – the magnetic domains point in random
direction; the magnetic effects of the atomic magnets cancel out so
there is no resultant magnetic effect
Phenomena
1. Magnetic saturation
‚Every magnet has a maximum strength when all the magnetic domains are
pointing in the same direction‛ – the magnet is magnetically saturated
2. Demagnetisation of magnets
Demagnetisation: the process of removing magnetism from a magnet
Ex; heating, hammering
‚They cause the atoms of the magnet to vibrate vigorously, mixing up
the directions of the magnetic domains.‛
3. Storage of magnets using soft iron keepers

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‚If we store magnets side by side, the magnets become weaker after some
time as ‘free’ poles near the ends of the magnet will repel one
another. The magnetic domains will be altered, weakening the magnets.‛
‚We store bar magnets in pairs by using soft iron keepers across the
ends of the bar magnets. The poles of the atomic magnets are in closed
loops with on ‘free’ poles to weaken the magnetic domains.‛
Ways of making magnets
1. Stroking method
***precaution is that the stroking magnet must br lifted sufficiently
high above the steel bar between successive stroke.
2. Electrical method using a direct current
‚When an electric current flows through the solenoid, it produces a
strong magnetic field which magnetizes the steel bar.‛
***The poles of the magnet is determined by the right-hand grip rule
Ways to demagnetising magnets
1. Heating
‚The atoms of the magnet vibrate vigorously when heated, causing the
magnetic domains to lose their alignment.‛
2. Hammering

27. 26 | P h y s i c
‚Hammering alters the alignment of the magnetic domains, causing the
magnet to lose its magnetism.‛
3. Electrical method using an alternating current
‚An alternating current is an electric current which varies its
direction many times per second. The magnet is then slowly withdrawn in
the East-West direction with the alternating current still flowing in
the solenoid.‛
A magnetic field: a region in which a magnetic object, placed within the
influence of the field, experiences a magnetic force
Magnetic field lines: invisible lines of force which we assume are
emerging from the North Pole and entering the South pole of the magnet
_ Magnetic field lines do not cross or intersect one another
_ the field lines drawn closer together represent strong magnetic fields
_ the field lines drawn further apart together represent weak magnetic
fields
***the point between two N poles is the neutral point
The earth’s magnetic field
A large imaginary magnet within the earth is believed to be caused by
convection currents inside the earth’s molten outer core
The imaginary ‘S’ pole is at the geographic north pole
The imaginary ‘N’ pole is at the geographic south pole
Magnetic shielding: a method of creating a region or space that is free
of magnetic fields by means of a closed loop of soft magnetic materials
_ use thin sheets of soft magnetic materials; they work by diverting the
magnetic fields

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‚Magnetic field lines tend to pass through magnetic materials easily.‛
Iron –soft magnetic material
_ gain and lose magnetism easily; strong induced magnet
_ induced magnetism occurs instantaneously either induced by another
magnet, or by a solenoid conducting electricity
_ loses its induced magnetism when the inducing magnet is removed
_ a temporary magnet; does not retain its magnetism
Steel –hard magnetic material
_ difficult to gain and lose magnetism; weak induced magnet
_ induced magnetism occurs slowly
_ does not lose its induced magnetism easily once steel is magnetised
_ a permanent magnet; retain its magnetism
‚A current-carrying conductor produces a magnetic field around it.‛
***using right-hand grip rule to find the direction of the magnetic
field around the wire
***the magnetic field of a long, straight current-carrying wire is
stronger when it is closer to the wire or when a large current flows
through the wire

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To increase the magnetic field strength at the centre of the flat coil
1. increase the current
2. increase the number of turns of the coil
To increase the magnetic field strength in a solenoid
1. increase the current
2. increase the number of turns per unit length of the solenoid
3. place a soft iron core within the solenoid; the soft iron core
concentrates the magnetic field lines, thereby increasing the magnetic
field strength
Uses of electromagnets
Circuit breaker

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_ When the current in a circuit increases, the strength of the
electromagnet will increase in accordance; this will pull the soft iron
armature towards the electromagnet.
_ As a result, the spring pulls apart the contact and disconnects the
circuit immediately, and the current stop to flow.
_ We can reconnect the circuit by using the reset button. The reset
button can be pushed to bring the contact back to its original position
to reconnect the circuit.
Motor effect
‚The force on the current-carrying conductor in a magnet field acts
perpendicular to both the direction of the current and the direction of
the magnetic field.‛
‚The force is reversed when we reverse the direction of the current or
magnetic field.‛
Fleming’s Left-Hand Rule
_ Thumb – motion
_ Forefinger – field
_ Second finger – current
Combined magnetic field when the wire is placed between the poles of the
magnet

31. 30 | P h y s i c
_ the combined field lines acting in the same direction gives a stronger
field than the combined field lines acting in the different direction 
force
Forces between two parallel current-carrying wires
‚Currents in opposing directions cause repulsion. Currents in similar
directions cause attraction.‛
To increase the turning effect on the wire coil in a magnetic field
1. increase the number of turns on the wire coil
2. increase the current in the coil – lower the resistance / increase
the voltage supply
3. insert a soft iron core into the coil to concentrate the magnetic
field lines
4. use stronger permanent magnet
The D.C. motor
_ electrical energy  mechanical energy

32. 31 | P h y s i c
Components
1. Rectangular coil connected in series to a battery and rheostat
2. Permanent magnets
3. Split-ring commutator
4. two carbon brushes
Split-ring commutator
; to reverse the direction of the current in the loop (coil every half a
revolution) whenever the commutator changes contact from one brush to
the other
Carbon brushes
; to conduct current to flow into and out of the coil
Electromagnetic induction: the phenomenon of inducing on electromotive
force (e.m.f.) in a circuit due to a changing magnetic field
The magnitude of this induced e.m.f. depends on;
1. the number of turns in the solenoid
2. the strength of the magnet
3. the speed inserting the magnet or withdrawing from the solenoid
Faraday’s law of electromagnetic induction
‚The e.m.f. induced in a conductor is proportional to the rate of
change of magnetic lines of force linking the circuit.‛

33. 32 | P h y s i c
Lenz’s law
‚The direction of the induced e.m.f., and hence the induced current in
a circuit, is always such that its magnetic effect opposes the motion or
change producing it.‛
***There is no e.m.f. generated when bar magnet is stationary
An A.C. generator: a device that uses the principle of electromagnetic
induction to transform mechanical energy into electrical energy
Alternation current generators (A.C. current)
_ the slip rings ensures that the direction of the induced current
flowing in the external circuit changes every half revolution
‚The induced e.m.f. is maximum when the coil in parallel to the
magnetic lines of force. The coil experiences the greastest changes in
magnetic field.‛

34. 33 | P h y s i c
‚The induced e.m.f. is zero when the coil in perpendicular to the
magnetic lines of force as the coil is not cutting through the magnetic
field lines. The coil experiences no changes in magnetic field.‛
To increase the induced e.m.f.
1. increase the numbers of turns on the coil
2. increase the frequency of rotation of the coil
3. use stronger permanent magnets
4. insert a soft iron core into the coil to concentrate the magnetic
field lines
The fixed coil A.C. generator is preferred over the simple A.C.
generator
1. Carbon brushes wear and tear easily
2. The connection with the slip ring becomes loose when the carbon brush
is eroded  increase the resistance at the connecting point  lesser
current is generated as it causes unnecessary thermal energy
3. The fixed coil A.C. generator design is more compact and space-saving
A transformer: a device that changes a high alternating voltage (at low
current) to a low alternating voltage (at high current), and vice versa
_ coil A induces e.m.f. in coil B, using A.C. current
_ this e.m.f. in turn drives an induced current to flow in coil B
Function of a transformer
1. Electrical power transmission
2. Regulating voltages for proper operation of electrical appliances
A closed-core transformer

35. 34 | P h y s i c
_ the lamination of the soft iron core reduces heat loss due to induced
eddy currents
A step-up transformer – Vs > Vp
A step-down transformer – Vs < Vp
***100% efficiency
Causes of power loss
1. heat loss due to the resistance of the coils
2. leakage of magnetic field lines between the primary and secondary
coils
3. heat loss due to eddy currents induced in the iron core
4. hysteresis loss caused by the flipping of magnetic dipoles in the
iron core due to A.C.
Reduce heat loss due to resistance
1. use thicker cables
2. reduce the current I, using a step-up transformer
( )
***Power can be transmitted more efficiently at higher voltages and
lower currents
Converting A.C. to D.C. – diodes
The diode: a semiconductor device that allows a current to flow easily
in one direction only

36. 35 | P h y s i c
Rectification: the conversion of A.C. into D.C.
Half-wave rectification
Full-wave rectification – a bridge rectifier

37. 36 | P h y s i c
Cathode-Ray Oscilloscope – C.R.O.
_ The electron gun emits a beam of electrons (thermonic emission) – a
cathode ray
_ The fluorescent screen is coated with Zinc sulphide
_ the Y-plates – vary the vertical position
_ the Y-plates – sweep the electron beam horizontally
Y-gain
_ amplifies the Y-deflection so that the small input voltages are
amplified before they are applied to the Y-plates
Time-base
_ controls the speed, at which the electron beam sweeps across the
screen horizontally from left to right– by the X-plates
_ sawtooth voltage applied to the X-plates

38. Physics Formula
Topic Formula SI unit Final unit
2.1: Kinematics Distance
Speed
Time

Distance (m)
Time (sec)
m/s
Displacement
Velocity
Time
 ;
s
v
t

Displacement (m)
Time (sec)
m/s
Diff. in Velocity
Acceleration
Time

Condition: Used only when acceleration is
constant.
Velocity (m/s)
Time (sec)
m/s
2
2.2 Dynamics Resultant Force Mass Acceleration 
F ma
Force (N)
Mass (kg)
Acceleration (m/s2
)
Newton (N)
2.3 Mass Weight
Density
W mg Mass (kg)
g = 10 N/kg
Newton (N)
(Density)
m
V
  ;.
Mass (g/kg)
Volume (cm3
/m3
)
g/cm
3
or
kg/m3
2.4 Turning Effect
of Forces
Moments Fd Force (N)
Perpendicular Distance (m)
Newton
metre (Nm)
Note: Perpendicular Distance is not always the length of the rod.
2.5 Pressure
Solids:
Force
Pressure
Area
F
A
 
Force (N)
Area (m2
)
N/m
2
, Pa
Liquids: Pressure h g h (m): Depth of Liquid
 (kg/m
3
): Density of liquid
g: 10N/kg
N/m
2
, Pa
Gases (when temp. is constant)
1 1 2 2PV P V
P (Pa): Pressure
V (m3
): Volume
NA
2.6 Energy, Work,
power
(Work Done)W Fd F (N): Force
d (Perpendicular dist): m
J
  21
. . Kinetic Energy
2
K E mv
m (kg): Mass
v (m/s): Velocity
J
 . . Potential EnergyP E mgh m (kg): Mass
g: 10N/kg
h (m): Height
J
X  
or Energy change
Power
Time
W
P 
Energy change /Work done(J)
Time (s)
J/s, W
(watt)
3.1 Principles of
Thermometry
0
100 0
X X
X X





(For Celsius scale only)
Theta: Unknown temperature
X0: “ice point”, X100: Steam pt
o
C
3.2 Thermal
Properties of
Matter
(heat energy)Q C C: Heat capacity J
Q mc m: mass
c: Specific Heat Capacity
J
fQ ml fl : Latent heat of fusion J
vQ ml vl : Latent heat of vapourisation J
4.1: General Wave
Properties
1
f
T

f: Frequency
t (sec): Time
Hz
v f  v (m/s): Velocity
 (m): Wavelength
f(1/t): Frequency
m/s
4.2: Light Snell’s Law:
sin
sin
i
n
r

n = refractive index (ratio)
i/r (o
): angle of
incidence/refraction
*Set calculator in degree mode.
NA. Ratio.
Condition: The angle of incidence must be in the less dense medium; angle r must be in the
denser medium.

39. 4.2: Light Ht of imageReal depth
Apparent depth Ht of object
c
n
v
  
c (m/s): Speed of light in vaccum
(3x108
m/s)
v (m/s): Speed of light in medium.
NA. Ratio.
1
sinc n
 c (o
): Critical angle. o
5.1: Current
Electricity
Q
I
t

I: Current (A)
Q: Charge (Columb)
t: Time (sec)
Coloumb,
C
W
Q
 
 : E.m.f. (Volts – V)
W: Work done/energy of circuit (J)
Q: Charge (Columb)
V, J/C
W
V
Q

V: Potential Diff. (V)
W: Work done/energy across
circuit component
Q: Amount of charge
V, J/C
Ohm’s Law: V IR
Condition: Only for ohmic conductors.
R: Resistance (  ) V
l
R
A

  m)
L: Length
A: Cross-sectional Area

5.2: Practical
Electricity
2
2 V t
E VIt I RT
R
  
J
2
2 V
P VI I R
R
  
W
5.3:
Electromagnetic
Induction
ps s
p p s
IV N
V N I
 