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J.C Physics Created by the class of…. • 3Br & 3Da • CBS Kilkenny 2012 STATIC ELECTRICTY Use simple materials to generate static electricty 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. 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 Magnetic 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 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 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 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. 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 WHITE LIGHT WHITE LIGHT IS MADE OF DIFFERENT COLOURS • Work hard • Play hard • Achieve the results you deserve. Mrs. Lenane 2012