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S1
Physics
What You Should Know
Forces
Forces can make things move, change speed or change shape.
Force is measured in units called Newtons (N).
To measure forces we can use a device called a Newton balance.
Mass is the amount of matter in an object. Mass is measured in kilograms (kg).
Weight is the force of gravity pulling an object towards the centre of the Earth.
Weight is measured in Newtons.
The weight of a certain mass on the surface of the earth can be calculated using the
formula:
weight = 10 x mass
Friction is a force which acts against the motion of an object. Friction is caused by
rough surfaces rubbing together.
Friction can be reduced by
(1)
(2)
(3)
(4)
Putting rollers or ball bearings between surfaces
streamlining car bodies
lubrication with oil
separating surfaces with an air cushion.
Friction can be increased by making surfaces in contact rougher.
Energy
You have already learned a lot about energy from the Science work you did in Primary
School. For example, you learned we get the energy to move about from the food we
eat. You may also have studied the properties of heat, light and sound.
Types of Energy
There are six main forms of energy, shown below with examples of that energy:
Heat energy
Light energy
Sound energy
Electrical energy
Movement energy
Stored energy
from burning wood
from a light bulb
from voice or loudspeaker
from a battery or socket
in windmills turning
in food, batteries or in fuel
Stored energy can be divided into three separate kinds:
Chemical energy
Potential energy
Nuclear energy
in food, fuel and batteries
in objects up high, springs and rubber bands
in nuclear power stations and atomic bombs
Energy Changers
Energy can be changed from one form to another. For example, in a Bunsen burner
stored energy changes to heat and light energy. Also, in a light bulb, electrical energy
changes to light energy.
This change can be shown as an energy transfer.
Starting energy
In a car: stored energy
In a drum:
movement energy



Finishing energy
movement energy
sound energy
Power Stations
Electricity is produced in power stations. A generator (or dynamo) is a machine that
changes movement energy into electrical energy. All power stations have a generator
to make electrical energy. The power station can either produce steam by burning
coal or gas or by the heat from a nuclear reactor. The steam has heat energy and
this can be used to turn a turbine that turns a generator that generates the
electricity.
In hydroelectric stations the moving water coming down pipes from the dam above
turns the turbines that turns a generator.
Once generated, the electricity is distributed by a system of power lines and pylons
called the National Grid.
Energy changes in the power stations
(i)
Hydroelectric power stations
stored (potential) energy
water behind dam
(ii)

movement energy
in pipes and turbine

electrical energy
in generator
In other Power Stations (coal, oil, gas or nuclear)
stored energy
fossil fuel or
nuclear fuel

heat energy
in steam

movement energy
in turbine

electrical energy
in generator
Energy resources
One major resource for energy is fossil fuels such as coal, oil and gas. Coal is made
from long dead plants while oil and gas were formed millions of years ago from tiny
sea plants and animals.
Renewable and non-renewable energy resources.
Fossil fuels such as coal, oil and gas are non-renewable fuels - once they are used up
there won't be any more.
Examples of renewable sources of energy are:
Hydroelectric, Wind, Solar, Wave, Tidal, Biomass and Geothermal.
Renewable energy sources will never run out and will always be available to generate
energy. The energy for most of the renewable sources comes from the sun (except
geothermal).
Electricity
Electric Charge
There are two types of electric charge: positive and negative. When something has an
electric charge on it the charge will be either positive or negative. If the charge on
an object is not moving we call this static charge.
When a charged object is near an uncharged object the two objects will be attracted
to each other. Charged objects attract uncharged objects.
When two charged objects are close together they will either attract or repel.
Opposite charges attract but like charges repel each other. So
positive and positive
negative and negative
positive and negative
Symbols and Circuits
Here are some symbols commonly used in circuits.
repel
repel
attract
Connecting up Circuits
An electric circuit is a path along which an electric current can flow.
For example, in a torch the circuit looks like this:
opened or closed to turn the bulb on or off.
Parallel and Series Circuits
Circuits can be either in Series or in Parallel.
If there is
a gap in the
circuit
electricity
will not flow
and the
bulb will not
light. The
switch is a
gap that
can be
Series:
Parallel:
In a series circuit, the bulbs get dimmer as more bulbs are added. Also,
if one bulb "blows" or is switched off, all the bulbs go out.
In a parallel circuit, the bulbs are brighter and each bulb can be switched
off without affecting the other bulbs. All the bulbs and appliances in
your house are arranged in parallel.
Current in series and parallel circuits
The size of the current flowing in a circuit is measured in amperes (A) or amps.
Current is measured using an ammeter. Current is measured in the circuit in series
with the component (see diagram below).
In a series circuit the current is the same at every point around the circuit.
In a parallel circuit the current from the supply splits up so that the currents in the
components add up to the current from the supply.
Voltage in series and parallel circuits
The size of the voltage
measured in volts (V).
Voltage is measured with
measured across (in
diagram below).
across a component in a circuit is
R
V
A
Voltmeter in parallel
measures voltage in volts
a voltmeter. Voltage is
Ammeter in series
parallel to) a component (see
measures current in amps
Batteries supply the voltage or energy to push the electricity around the circuit. The
voltage in a circuit can be increased by connecting more than one battery (all facing
the same way).
In a parallel circuit the voltage across all the components is the same as the battery
voltage.
In a series circuit the voltages across the different components will add up to the
battery voltage.
Space
A galaxy is a large cluster of billions of stars (e.g. the Milky Way).
A star is a large ball of (mostly) hydrogen that is undergoing nuclear fusion and emitting
light and heat. The sun is a star.
The sun and many other stars have a solar system. A solar system consists of a central
star orbited by planets. The sun and the eight planets that orbit around it make up our
solar system.
A planet is a large ball of matter that orbits a star (e.g. Earth or Jupiter). Planets do
not emit light themselves. Planets can be seen because they reflect light from the sun
Many planets have moons. A moon is a lump of matter that orbits a planet
The Solar System
The eight planets are grouped in many different ways. Two easy groupings are
composition (what they are made up of) and size.
The rocky planets are mostly made up of rock and metal. These planets are very dense
and move quickly around the Sun. These planets have small diameters. They also do not
have rings and very few moons.
The rocky planets are Mercury, Venus, Earth, Mars.
The gas giant planets are mostly made up of gases (hydrogen and helium). These planets
are very large and move slowly around the Sun. They all have rings and many moons.
The gas giant Planets are Jupiter, Saturn, Uranus, Neptune.
Exoplanets and Habitable Zones
An exoplanet is a planet outside of our solar system that orbits a star other than our
Sun.
The habitable zone around a star is the region where the liquid water may exist. The
earth orbits the sun in the middle of the sun’s habitable zone.