Transcript Junior Cert Physics powerpoint

J.C Physics
Created by the class
of….
• 3Br & 3Da
• CBS Kilkenny 2012
STATIC ELECTRICTY
Use simple materials to
generate static electricty
Build up of charge
Method
1.Rub a plastic biro against the sleeve of
your jumper
 2.The biro will pick up small pieces of
paper

Conclusion

This happens because the pen becomes
negatively charged. 
Also see page 362 in textbook
See page 319 in textbook
Conversion of Electrical
Energy to Magnetic to
Kinetic Energy

Method
Method
Connect 6 V battery to nail
 Wrap wire around nail
 Turn on battery
 Put nail near paper clips

Results

The nail was magnetised. It picked up the
paper clips
Perspex
rod
wire
A conductor is a material through which an electrical
charge can flow.
An insulator is a material through which an electrical
charge cannot flow.
To see if a piece of wire conducts
electricity
 Set up the circuit.
 Connect the wire to the circuit as shown
on in the diagram. An additional wire is
inserted here
Result – the light bulb will light up showing that
wire is a conductor of electricity
To see if a Perspex rod conducts
electricity
 Set up the circuit as before.
 Replace the wire with a Perspex rod.
Insert a Perspex rod here
instead of the wire
Result – the light bulb will not light up showing that
the Perspex rod is not a conductor of electricity
To Plot the Magnetic Field of a
Bar Magnet
Equipment:1 Bar magnet,2
Science books ,a Sheet of plain
paper, iron filings .
Step
1:Wedge the Bar magnet
between the the two books.
Step
2:Place the sheet of paper
over the two books .
 Step 3 ;Sprinkle the iron filings over
the sheet and watch for result
 Result ; A picture of the magnetic
poles should be visibly clear
 POD
Series &
Parallel Circuit
What it is…
•Bulbs are arranged one after another.
•If you remove 1 bulb the other won’t
work.
•The current in the battery divides.
•Some current passes through one bulb
and the rest through the second.
•If the bulbs are identical the current
equally divides.
Examples
 Headlights
in a car are parallel.
 Christmas lights are both series
and parallel.
 If you remove one bulb and it all
goes off then it is a series circuit.
 If not then it is a parallel cricuit.
Calculating
V
= voltage
I = current
R = resistor
Amps measured with
Ammeter
1. Connect the Battery and the
Ammeter together
2. Attach a lamp onto the circuit
3. Observe
Measuring Voltage with a voltage
meter
 1.Connect the voltage meter , battery and
bulb into a circuit
 2. Observe the results on the voltage meter
Resistance
 Measured using an ohmmeter.
 Units= ohms
DIRECT CURRENT (D.C)
• A current that flows in one direction only.
Alternating current (A.C)
• A current that is continually
changing in direction
Domestic Voltage
supply
• 240 volts
The chemical effect of an electric
current
•Is the charging of a phone
•The magnetic effect of an electric
current
•Is the speaker of a stereo
•The heating effect of an electric current
•Is the shower
What happens a LDRs
resistance measure under
varying degrees of light
brightness
 1.If bright light falls on a LDR the
resistance is low . A larger current can
flow through the resistor .
 2.If dim light falls on a LDR the resistance
is high . A smaller current will now flow
through the resistor .
 3.Using a LDR you can arrange for an
electrical appliance to be controlled by
light . In fact,some appliances can be
switched on or switched or switched off by
simply shining light on the LDR connected
to them .
Unit of electrical energy =
kilo watt-hour {kWh}
Name 3 wires in a plug =
earth/live/neutral
WORK,POWER AND
ENERGY
Work= force x distance
Force= Newtons (N)
Distance= Metres (m)
Work=joules (J)
Advantages + Disadvantages
Non-renewable sources of energy are sources
that will eventually run out another name
for them is fossil fuels e.g. Oil + gas etc.
Advantages;
 Easy to get.
 Reasonably cheap.
Disadvantages;
 Causing greenhouse gas emissions.
 Polluting the atmosphere e.g. Acid Rain.
Because fossil fuels are finite , we try to
improve our efficiency of the renewable
sources of energy.
Examples;
 Solar Energy
 Hydro Electricity
 Wind Energy
 Nuclear Energy
Solar energy is taken straight from the rays of the
sun. We convert solar energy to electrical
energy using Solar Cells. We also convert
energy to heat energy using solar panels.
Advantages;
 Solar energy is free.
 Solar energy does not cause pollution.
Disadvantages;
 The efficiency of solar cells needs to be
improved as only a small percentage of energy
is converted to electrical energy.
By building a dam in a large river it is possible to build
a vast amount of water. This water has potential
energy when stored behind the dam wall. When the
water is released it becomes kinetic, this kinetic
energy is changed into electrical energy
Advantages;
 Does not cause pollution.
 cost efficient way to produce energy.
Disadvantages;
Flooding can destroy plant + animal habitats.
On a windy day, the moving air has a large
amount of kinetic energy. The idea is to
change this kinetic energy to electrical
energy.
Advantages;
 Does not cause pollution.
 Wind energy is free.
Disadvantages;
No electricity produced on a clam day.
Nuclear energy is usually considered as renewable
energy. One form, nuclear fission, uses materials
like Uranium. Uranium is finite.
However another fusion is used with the basic
material , water. However the technology for
generating electricity from nuclear power is not
yet available.
Advantages;
 Nuclear fusion would use a fuel in plentiful
supply.
 Nuclear energy would reduce the greenhouse
emissions.
Tidal and Wave Energy;
The kinetic energy of the waves and the tide
is converted to electrical energy.
Geothermal Energy;
Heat energy can be trapped beneath the
surface of the Earth. This heat can also be
used to heat homes or converted to
electrical energy.
Biomass Energy;
Some plants grow very quickly e.g. Sugar
SOURCES
OF
ENERGY
PAGE 316 IN YOUR TEXT
BOOK BY pierce cody
Non-Renewable Sources
of Energy
Non-renewable sources of
energy are sources that will
eventually run out. These
sources are called fossil fuels
for example
1.OIL
2.COAL
3.GAS
4.TURF
Advantages and
Disadvantages of nonrenewable
Advantages
1. Easy to get
2. Reasonably cheap
Disadvantages
1. Causing greenhouse gas emissions
2. Polluting the atmosphere
Renewable sources of
energy
• Fossil fuels will eventually run out.
Because of this we try to improve
the efficiency of the renewable
sources of energy. Examples pf
renewable sources of energy
include:
• solar energy
• hydro-electricity
• wind energy
• nuclear energy
Example of renewable
energy = SOLAR
ENERGY
Advantages
1. Solar energy is free
2. Solar energy does not cause pollution
Disadvantages
1. The efficiency of solar cells needs to be
improved
2. Solar cells are expensive to make
Converting Light
energy to Electrical
energy to Kinetic
energy
By Declan Wall



Connect the solar cells to the solar motor
Shine light from the lamp onto the solar
cells
See page 320 in text book
Conclusion

The light energy from the lamp was
converted to electrical in the solar cells
which was converted to kinetic energy in
the moving fan
Levers are designed to lift
objects with less effort than
you would have on your
own.
Modern day uses for levers
are in some cranes and
heavy machinery.
The effort is where the lever gets
its input.
For example, on a tweezers, the
part you push down on is the
effort.
The load is the item being moved
by the lever.
For example, a tractors loader
lifting a bale, the bale is the load.
The fulcrum is the point where
the lever pivots.
For example, the wheel on a
wheelbarrow is the fulcrum.
Why do objects float on water?
Objects float on water because
the object is less dense than the
liquid.
What is meant by force?
Force causes a stationary object to
move.
What is the unit of force?
The unit of force is newton and the
symbol is N.
PRESSURE
What is Pressure
• Pressure is force per unit area
• Pressure = Force divided by Area
• The pressure due to a force depends on two
things
 Pressure increases when the force increase
 Pressure increases when the area that the force
is acting on decreases
• Pressure is measured in newtons per metre
squared.
Pressure
Mathematical Example
A stone block of weight 225000N is to be used as
a base for a sculpture. The block has dimensions
3m x 2m x 1.5m.
(i) What is the greatest possible pressure that the
block could exert on the ground
(ii) What is the least possible pressure that the
block could exert on the ground
Pressure in Liquids
• Why do divers need to wear protective
suits when diving?
• It is because the weight of the water above
them exerts a great pressure. The diving
suits stops the diver being squashed.
• If a diver comes up too quickly the change
in pressure can be very dangerous.
Bubbles of nitrogen form in the blood. This
is a condition known as the bends
Atmospheric Pressure
• Air is made up of particles of various gases.
These are attracted to the earth by gravity thus
they have a weight.
• The pressure due to the weight of air pressing
down on the earth is called atmospheric
pressure.
• This pressure acts on our bodies but luckily the
pressure inside our body exerts an equal
pressure outwards to balance this.
Atmospheric Pressure
• As we increase our height above sea level the
atmospheric pressure decreases.
• Our ears ‘popping’ is our body’s way of
equalising the pressure on either side of our ear
drum.
• In space there is no atmospheric pressure so the
pressure from inside our body would have no
outside pressure to balance in. This means
astronauts might explode without special suits!!
Measuring Pressure
•
A barometer is an instrument used to
measure atmospheric pressure.
• There are two types of barometer:
(i) Mercury
(ii) Aneroid
Normal atmospheric pressure is written as
76cm of mercury
Atmospheric Pressure and
Weather
• The atmosphere is like a blanket around
the earth. It is like a ‘sun block’ for the
earth.
• Atmospheric pressure changes with the
weather.
• Isobars joins places of equal pressure. If
the isobars are close together winds will
be strong. If far apart winds will be light
Atmospheric Pressure and
Weather
• If the pressure over a particular area is
high it will mean fine weather.
• Low pressure areas will generally be
windy and wet.
Using Pressure
• Hydraulics – As pressure is passed
through a liquid it does not change
Atmospheric Pressure
varies with height
• The atmosphere is a fluid.
• Therefore the pressure in the
atmosphere is affected by
depth.
• Depth and height are
opposite – the greater the
depth the lower the height.
• Pressure increases with
depth so therefore the lower
the height the greater the
High Pressure
Atmospheric pressure affects the weather.
High Pressure causes:
• Calm, clear sunny dry days and
calm clear dry starry nights.
• Hot days and cool nights in
summer.
• Cold frost nights in winter.
Low Pressure
Low Pressure causes:
• Windy, cloudy, very humid and wet
days
• and nights.
• Cool days and nights in summer.
• Mild days and nights in winter.
Why do objects float on water?
Objects float on water because
the object is less dense than the
liquid.
What is meant by force?
Force causes a stationary object to
move.
What is the unit of force?
The unit of force is newton and the
symbol is N.
FRICTION
:There is friction between the brake pad and the wheel of the bike. This is
what stops the bike
:There is friction between a moving car and the air. This friction is overcome
by the force of the engine
LUBRICATION
:This is used to reduce the friction between two surfaces in contact
e.g. bones at the joint are surrounded by a fluid that acts as a lubricant
HOOKE’S LAW
The extension of an elastic body is directly proportional to the force causing
the extension
This is proved by stretching a spring with different weights. Graph these
weights with the length the spring has extended . The points should make a
straight line through the origin . This proves that the extension of an elastic
body is directly proportional to the force causing the extension
Heat
Difference between heat and temperature
Difference between heat and
temperature





Heat
Heat is a form of energy.
The unit used for heat is the joule (J)
Temperature
Temperature is a measurement of the hotness
of a body.
 The unit used for temperature is the degree
Celsius (C)
Latent Heat
 Causes a change in state and not a change in
temperature.
 A solid might change to a liquid or a liquid might
change to a gas.
Conduction
 Transfer of heat through a solid.
 Particles in the solid vibrate & transfer heat
from one particle to another by conduction.
 Experiment
Conduction continued
 Attach wax to the end of each rod
 Pour boiling water into metal container
 The wax that melts on the rod first before
any other, is the best conductor of heat.
 Result: Wax melts from the copper rod
first.
EXPANSION OF SOLIDS
WHEN HEATED AND
CONTRACT WHEN COOLED
METHOD
 1. SEE IF BALL FITS INTO RING.
 2. THEN HEAT THE BALL WITH
BUNSEN.
 3. SEE IF BALL FITS INTO RING AGAIN
RESULT
 THIS SHOWS THAT WHEN A SOLID IS
HEATED IT EXPANDS.BALL DID NOT
FIT THROUGH RING.
 AND WHEN COOLED
CONTRACTS.BALL FITS THROUGH
RING.
EXPANSION OF LIQUIDS
WHEN HEATED AND
CONTRACTION WHEN
COOLED
EXPERIMENT
METHOD
 Fill a round bottomed flask with water
that has been coloured.
 Insert stopper with glass tube on top
of flask.
 Hold flask with clamps.
 Heat water with bunsen burner.
result
 The coloured water rises up to the top of
the test tube, due to heat (expansion).
Heat and solids
The equipment needed from this is retort stand, ball and ring
apparatus, Bunsen burner that is what is needed for this
experiment.
Heat is a form of energy.

To test how to see that the ball fits
through the ring is when it is heated it
expands but when it is cooled it contracts
so it will fit through the ring. The ball
must cool for 10 minutes before doing the
experiment. The ball should fit through
the ring.
Conclusion

The solid ball expanded when heated and
contracted when cooled.
Result 1

The ball does not fit through the ring as it
expanded due to heat. Allow the ball to
cool for about 10 minutes. See if the ball
fits through the ring now that it has
cooled.
Result 2

The ball now fits through the ring as it has
contracted due to cooling.
Heat and solids
The equipment needed from this is retort stand, ball and ring
apparatus, Bunsen burner that is what is needed for this
experiment.
Heat is a form of energy.
 To test how to see that the ball fits through
the ring is when it is heated it expands but
when it is cooled it contracts so it will fit
through the ring. The ball must cool for 10
minutes before doing the experiment. The
ball should fit through the ring.
Conclusion
 The solid ball expanded when heated and
contracted when cooled.
Result 1
 The ball does not fit through the ring as it
expanded due to heat. Allow the ball to cool
for about 10 minutes. See if the ball fits
through the ring now that it has cooled.
Result 2
 The ball now fits through the ring as it has
contracted due to cooling.
To investigate conduction and
convection in water
experiment
Method
Sink an ice cube to bottom of a test tube of
water with the help of a weight (coin).
 Heat the water at the top of the test tube
with bunson burner.

Result 1
The water at the top of test tube can be
boiling but the ice has not melted
 Heat doesn’t travel down the water
 Water is a poor conductor.

Result 2
Remove coin and let ice float to the top of
the test tube.
 Heat the bottom of the test tube with
bunsen burner.
 Heating the bottom will melt the ice.
 Heat travels in water by convection.

EXPANSION OF GASES
WHEN HEATED
EPUIPMENT 
.Retort stand
.Round-bottomed flask
.Bunsen burner
.Glass tube
.Beaker of water with coloured food dye.
Expansion of gases
METHOD 
1. Insert a stopper with a glass tube into the
top of the flask.
2. Set up the apparatus with the retort stand.
3. Gently heat the round bottomed flask.
Observe the glass tube.
RESULT 
.The coloured water rises in the glass tube. As
the air contracts the water is pulled up.
Why is the sun our primary
source of energy
 Without the sun we would not have fossil
fuels, when alive these plants and animals
needed the sun.
 Photosynthesis is needed for plants.
Law of conservation of energy
 Energy is neither created nor destroyed but
can be converted from one form to another.
Luminous objects

Luminous objects give out light
Non luminous

Non luminous objects reflect light
REFRACTION
Refraction of light is the bending of light as it
passes from one medium to another.
REFLECTION
LIGHT : Light can be reflected off almost
every surface. It allows us to see nonluminous objects like books
 SOUND : Sound reflects of certain
surfaces and a good surface to reflect
sound would be a smooth wall. An echo is
an example of sound reflection.

SOUND AS A FORM OF ENERGY

SOUND AS A FORM OF ENERGY :
When you hear someone talk at the far
side of a room, sound energy travels from
your vocal chords to your ears.
HOW SOUND IS PRODUCED
SOUND IS PRODUCED BY VIBRATIONS
 Sound is made by vibrations as a speaker
vibrates and produces a sound. The
reason we have a problem seeing them is
because they move very fast and we cant
see them but it is possible to see them.

WHITE LIGHT
 WHITE LIGHT IS MADE OF
DIFFERENT COLOURS
• Work hard
• Play hard
• Achieve the results you
deserve.
Mrs. Lenane 2012