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# Energy,elec.&forces

{Consider the energy transfers in the simple electric circuit:http://www.bbc.co.uk/bitesize/ks3/science/images/electric_circuit.gif}. We can show the transfers(of a simple electric circuit like this: battery (store of [] energy chemical energy) (transferred as [] energy electrical energy) → lamp (transferred as [] energy light energy) → surroundings.
The light energy that the lamp of an electrical circuit transfers into its surroundings is useful, unlike the [] energy that it also transfers into the surroundings thermal
The battery is a [] of chemical energy store. The energy is transferred to the lamp by . electricity , which transfers the energy to the surroundings by light.
{[http://www.bbc.co.uk/bitesize/ks3/science/images/sankey.gif]|| Sankey diagrams summarise all the energy [] taken place in a process transfers. The thicker the line or arrow, the greater the amount of involved energy. Notice that the total amount of energy transferred to the surroundings is the same as the amount of electrical energy. We say that the energy has been conserved. Energy is 'always'
Moving things have [] energy kinetic energy. The [] a thing is and the [] it moves - the more kinetic energy it has. The heavier a thing is and the faster it moves
Instruments transfer energy to the air as sound. [] energy from the moving air [] transfers the [] energy to your []. Kinetic energy from the moving air molecules transfers the sound energy to your eardrum.
Thermal energy is what we call energy that comes from heat. A cup of hot tea has thermal energy in the form of kinetic energy from its particles.
Some chemical reactions release energy. For example, when an explosive goes off, chemical energy stored in it is transferred to the surroundings as [] energy, [] energy and [] energy.
A battery transfers stored [] energy chemical energy as electrical energy in moving charges in wires. For example, electrical energy is transferred to the surroundings by the lamp as [] energy and [] energy. light energy and thermal energy.
A rock on a mountain has store energy because of its p[] position above the ground and the [] of [] pull of gravity. This energy is called gravitational potential energy.
If an object fell, it would release a type of energy known as gravitational potential energy. As the rock falls to the ground, the gravitational potential energy is transferred as kinetic energy.
Heat and temperature are not the same thing, although both are concerned with [] energy. thermal energy. The heat an object contains is the amount of its thermal energy, measured in joules(J).
The temperature of an object is to do with how [] or [] it is hot or cold it is, measured (usually) in degrees Celsius(°C). A [] is used to measure the temperature of an object thermometer.
A swimming pool at 30°C is at a lower temperature than a cup of tea at 80°C. The swimming pool contains more water, so it stores [] thermal energy more. It takes longer to boil a large beaker of water than a small beaker because the large beaker contains more water and needs more thermal energy to reach 100°C.
We get energy from many different types of energy resources, including fuels, food and stores of energy such as batteries or the wind. We can divide energy resources into two categories: renewable and non-renewable. Renewable energy resources can be replaced. ('Non-renewable energy resources cannot be replaced once they are all used up.')
Biomass fuels come from living things. (Wood is a biomass fuel). (Biomass full are a renewable resource).
Wind power: moving air has huge amounts of [] energy kinetic energy, and this can be transferred into electrical energy using wind turbines. ('Wind turbines cannot work...if the wind speed is so high it would damage them.')
Water power: moving water has [] energy kinetic energy. This can be transferred into useful energy in different ways. For example: wave machines use the up and down movement of waves to turn electricity [] generators; tidal barrages are built across the mouths of rivers, as water moves in or out of the river mouth when the tide turns, the [] energy in the water is used to turn electricity generators kinetic.
Hydroelectric power (HEP) schemes store water high up in dams. The water has [] [] energy gravitational potential energy which is released when it falls. As the water rushes down through pipes, this stored energy is transferred to kinetic energy, which turns electricity generators that transfer energy to power lines in the form of electrical energy. || http://www.bbc.co.uk/bitesize/ks3/science/images/energy_transfer3.gif
Geothermal: In some places the rocks underground are hot. Deep wells can be drilled and [] water pumped down cold water pumped down. The water runs through fractures in the rocks and is heated up. It returns to the surface as hot water and steam, where its energy can be used to drive turbines and electricity generators
{Solar cells are devices that convert light energy directly into electrical energy. (You may have seen small solar cells on calculators. Larger arrays of solar cells are used to power road signs, and even larger arrays are used to power satellites.)}
Solar panels are different to solar cells. Solar panels do not generate e[] electricity. Instead they heat up [] directly. water directly. A pump pushes cold water from a storage tank through pipes in the solar panels. The water is heated by [] energy from the Sun and returns to the tank. (They are often located on the roofs of buildings where they can receive the most sunlight.)
Most of the UK's electricity is generated in power stations using fossil fuels. [] energy released from the burning fuel is used to boil water to make steam thermal--, which expands and turns turbines. These drive the generators to produce electricity. (The electricity goes to the transformers to produce the correct voltage).
As the fossil fuels are non-renewable energy resources, and they also produce p[] when they burn. pollution. Using renewable energy resources will reduce the rate at which the fossil fuels are
Forces can be measured using a [] meter force meter. Force meters contain a spring connected to a metal hook. The spring stretches when a force is applied to the hook. The bigger the force applied, the longer the spring stretches and the bigger the r[] reading. The unit of force is called the newton, and it has the symbol N.
Weight is a f[] force, and is measured in newtons. Mass is measured (usually) in kilograms (kg).
The mass of an object is the amount of [] it contains matter. The more matter an object contains, the greater its mass. (An elephant contains more matter than a mouse, so it has a greater mass.) An object's mass stays the [], wherever it is wherever.
All objects have a force that attracts them towards each other. This is called gravity. ('Even you attract other objects to you because of gravity, but you have too little mass for the force to be very strong'.)
Gravitational force increases when the [] are bigger masses-- or when the [] are closer objects. ('Gravity only becomes noticeable when there is a really massive object... We are pulled down towards the ground because of gravity. The gravitational force pulls in the direction towards the centre of the Earth.')
pressure = force/area, P= F/A.
The unit of pressure is notated as either N/m^2 or pascal. (The pressure, where there is a force of 20 N acted over an area of 2 m^2 is 10 N/m^2 or 10 Pa.)
We can show the forces acting on an object using a force diagram. In a force diagram, each force is shown as a force arrow. The longer the arrow, the [] the force bigger.
T~he direction in which a force acts is shown on a force diagram by a force arrow. The arrow is usually labelled with the force's n[] and its s[] name and its size (in newtons). (Text books often show a force with a thick coloured arrow, but it is best if you just use a pencil and ruler to draw an arrow with a single line.)
When two forces acting on an object are equal in size but act in opposite directions, we say that they are [] forces balanced forces.
If the forces on an object are balanced (or if there are no forces acting on it): an object that is not moving stays still, an object that is moving continues to move at the same [] and in the same [] at the same speed and in the same direction. (Notice that an object can be moving even if there are no forces acting on it).
The forces on a hanging crate are the [] of the rope and the [] of the crate the pull of the rope and the weight of the crate. The forces on the hanging crate are equal in size but act in opposite directions. The weight pulls down and the tension in the rope pulls up.
Objects float in water when their weight is balanced by the [] from the water upthrust from the water. The object will sink until the weight of the water it pushes out of the way is the same as the weight of the
When an object rests on a surface, its weight is balanced by the reaction force from the surface. The surface pushes up against the object. ('The reaction force is what you feel in your feet as you stand still. Without this balancing force you would sink into the ground.')
When two forces acting on an object are not equal in size, we say that they are unbalanced forces. If the forces on an object are unbalanced: an object that is not moving starts to move, an object that is moving changes [] or [] speed or direction.
The size of the overall force acting on an object is called the resultant force. If the forces are balanced, this is zero. The resultant force is the [] between the two forces difference. (If 100 N is acting in one direction and 40 N is acting in an opposite direction: the resultant force is 60 N.)
Whenever an object moves against another object, it feels [] forces frictional forces. These forces act in the opposite direction to the movement. Friction makes it harder for things to
Frictional forces are much [] on smooth surfaces than on rough surfaces smaller-- (which is why we slide on ice).
When there is a lot of friction between moving parts, energy is lost to the surroundings as heat. (When you rub your hands together, friction warms them up.)
Bikes, cars and other vehicles, as they move, experience [] resistance air resistance. The faster the vehicle moves, the [] the air resistance becomes bigger. The top speed of a vehicle is reached when the force from the cyclist or engine is [] by [] [] balanced by air resistance.
Air resistance is caused by the [] forces frictional forces of the air against the object.
Racing cyclists crouch down low on their bikes to reduce the [] [] on them air resistance on them. This helps them to cycle faster. They also wear streamlined helmets. These have special, smooth shapes that allow the air to [] over the cyclist more easily. flow.
Forces can make objects turn if there is a pivot. Turning forces around a pivot are called moments. A see-saw will balance if the moments on each side of the pivot are equal. ('This is why you might have to adjust your position on a see-saw if you are a different weight from the person on the other end.'). If a nut is difficult to undo with a short spanner, a longer spanner will help, as the nut will have a bigger moment, when the force is applied further from the pivot. (Using the same principle you can increase the moment applied by a lever or a crowbar, and this can help you move heavy objects more easily.)
moment = force x distance.
The unit of moment is notated Nm (the moment where a force of 10 N is acting 2 metres from the pivot is 20 Nm (newton metre)).
{'Have you ever heard a crackle when taking off your jumper?' This is caused by tiny electric charges on your clothes. It's called static electricity. Your jumper and shirt get electrically charged as they rub together, and then [] electric charges [] negative electric charges jump (from one to the other). (This makes sparks that crackle - you can even see them in a dark room.)}
When electric charges move in a wire, we say that an electric [] flows in the wire current. For an electric current to flow, we 'need' two things: something to make the electricity flow (such as a battery or power pack), and a complete [] for the current to flow in path--(which is called an electric circuit).
An electric current will not flow if we do not have a power source (eg. a cell, a power pack). It also won't flow if the circuit is not complete. One end of the power source must be joined to the other end by the [] and components of the circuit wires.
There are two types of circuit we can make, called series and parallel. The components in a circuit are joined by wires; if there are no branches, then it's a series circuit, and if there are branches - it's a parallel circuit.
If you put more lamps into a series circuit, the lamps will be [] than before dimmer. In a series circuit, if a lamp breaks or a component is disconnected, the circuit is broken and all the components stop working. Series circuits are useful if you want a warning that one of the components in the circuit has failed. They also use less wiring than
In a parallel circuit, if a lamp breaks or a component is disconnected from one parallel wire, the components on different branches keep working. And, unlike a series circuit, the lamps stay bright if you add more lamps in parallel. Parallel circuits are useful if you want everything to work, even if one component has failed. (This is why our homes are wired up with parallel circuits.)
Current is a measure of how much electric [] flows through a circuit charge. The more charge that flows, the bigger the current. Current is measured in units called amps. The symbol for amps is
A device used to measure current is an Ammeter. To measure the current flowing through a component in a circuit, you must connect the ammeter in [] with it series.
Voltage is a measure of the difference in [] [] between two parts of a circuit electrical energy. The bigger the difference in energy, the bigger the voltage.
Voltage is measured in volts. The symbol for volts is V. Voltage is measured using a voltmeter; to measure the voltage across a component in a circuit, you must connect the voltmeter in [] with it parallel. You can measure the voltage across a cell or battery. The [] cells, the bigger the voltage more.
The current is the same everywhere in a series circuit (it does not matter where you put the ammeter, it will give you the same reading), as the circuit is not [] up used. The current in a series circuit depends upon the number of cells.
Bar magnets are permanent magnets. This means that their magnetism is there all the time and cannot be turned on or off. They have two poles: north pole and south pole. The north pole is the []-seeking pole and the south pole it the []-seeking pole north---south. Unlike poles attract, and like poles
You can only show that an object is a magnet if it repels a known magnet. (Seeing if it sticks to a magnet is not a good test, because unmagnetised iron, steel, cobalt and nickel objects will be attracted to either pole of a magnet).
Magnets create [] fields magnetic. They fill the space around a magnet where the magnetic forces work, where they can attract or repel [] materials magnetic.
In diagrams of magnetic fields: the field lines have [] on them, arrows--, the field lines come out of 'N' and go into 'S', the field lines are more concentrated at the poles.||[http://www.bbc.co.uk/bitesize/ks3/science/images/magnetic_fields.gif] (It would be difficult to draw the results from the sort of experiment seen in the photograph, so we draw simple magnetic field lines instead.)
When an electric current flows in a wire it creates a [] field around the wire magnetic. By winding the wire into a [] we can strengthen the magnetic field coil. [] are made from coils like this. Electromagnets
We can make an electromagnet stronger by: wrapping the coil around an iron core, adding more [] to the coil turns and increasing the [] flowing through the coil current.
The magnetic field around an electromagnet is just the same as the one around a [] magnet bar. It can, however, be reversed by turning around the battery. The magnetism of electromagnets can be turned on and off just by closing or opening the
The magnetic field around an electromagnet is just the same as the one around a [] magnet bar. It can, however, be reversed by turning around the battery.
Light carries energy and travels as a wave at a speed of 300,000,000 meters per second. When unmanipulated, light travels in lines that are straight.
Energy transfer diagrams show the locations of both energy [] and energy [] energy stores and energy transfers.
Created by: Toluo