Do now! 1 Energy Types Word Scramble 2 Title – Energy Flow diagrams and the date

Some examples of forms of energy Kinetic energy (KE) Energy due to a body’s motion. Potential energy (PE) Energy due to a body’s position Thermal energy Energy due to a body’s temperature. Chemical energy Energy associated with chemical reactions. Nuclear energy Energy associated with nuclear reactions. Electrical energy Energy associated with electric charges. Elastic energy Energy stored in an object when it is stretched or compressed. All of the above forms of energy (and others) can ultimately be considered to be variations of kinetic or potential energy.

Learning Today Energy flow diagrams Energy flow circus Sankey diagrams Potential Energy – P.E. Homework Potential Energy Sheet

Other energy measurement examples 4200 joules (4.2 kJ)1 food Calorie J (1 MJ)Energy of a Mars bar JEnergy need to produce a syllable of a word J Energy received by the Earth from the Sun in one day

Conservation of energy Energy cannot be created or destroyed. It can only be transformed from one form to another form. Conservation of energy also means that the total energy in the universe stays constant.

Energy Flow diagrams – Copy please Energy flow diagrams show energy transformations. Work done = energy transformed For example, when a car brakes, its kinetic energy is transformed into heat energy in the brakes. Kineticheat

02/07/2015 Energy changes To describe an energy change for a light bulb we need to do 3 steps: Electricity Light + heat 1) Write down the starting energy: 3) Write down what energy types are given out: 2) Draw an arrow Draw energy flow diagrams for the following…? 1)An electric fire 2)A rock about to drop 3)An arrow about to be fired

Television electrical light sound heat What are the main energy transfers for a television (don’t forget the wasted energy)?

Car engine chemical kinetic sound heat What are the main energy transfers for a car engine (don’t forget the wasted energy)?

Radio electrical sound heat What are the main energy transfers for a radio (don’t forget the wasted energy)?

Pendulum oscillation GRAVITATIOINAL POTENTIAL ENERGY KINETIC ENERGY MAXIMU M MINIMU M MAXIMU M ZER O The total energy, gravitational potential plus kinetic, remains the same if there are no significant resistive forces

Wasted sound energy Can you name some devices that waste energy as sound? _____________ Hairdryer Washing machine Car engine Computer Microwave Bunsen burner Wind turbine Dish washer

Wasted heat energy Can you name some devices that waste energy as heat? _____________ Computer Turbine Motor Transformer Any electrical device Television Radio Car engine

What happens to wasted energy? Wasted e_____ spreads out (d_______) into the s_________. This makes the energy harder to r____. Remember energy can not be c______ or d_______. What happens to the wasted energy you get whenever energy is changed from one form to another? This is why it is important to r_____ the amount of wasted energy there is.

02/07/2015 Energy Transfer diagrams Consider a light bulb. Let’s say that the bulb runs on 100 watts (100 joules per second) and transfers 20 joules per second into light and the rest into heat. Draw this as a diagram: 100 J/s electrical energy “Input” energy“Output” energy 80 J/s heat energy (given to the surroundings) 20 J/s light energy

02/07/2015 Example questions Consider a computer: 150 J/s electrical energy 10 J/s wasted sound 20 J/s wasted heat Useful light and sound 1)How much energy is converted into useful energy?

Here is a more complex energy transformation diagram, the sort used by engineers. This one is for an aeroplane engine. 02/07/2015

Choose appropriate words to fill in the gaps below: Energy is required to do ________. Energy is measured in ________ (J) Energy cannot be created or ___________ but can only change ________. Kinetic energy is the energy possessed by __________ bodies. When an object is lifted up it gains gravitational _____________ energy. Heat or __________ energy is often produced as a _________ energy form, dissipated to the surroundings. work form movingjoulespotentialthermal destroyed WORD SELECTION: wasted work form moving joules potential thermal destroyed wasted

02/07/2015 Gravitational Potential Energy Gravitational potential energy is the energy an object has because of its position in a gravitational field GPE = Weight x Change in height (Joules) (newtons) (metres) GPE HH W

02/07/2015 Gravitational Potential Energy Gravitational potential energy is the energy an object has because of its position in a gravitational field GPE = Weight x Change in height (Joules) (newtons) (metres) GPE HH W

02/07/2015 Some example questions… How much gravitational potential energy have the following objects gained?: 1.A brick that weighs 10N lifted to the top of a house (10m), 2.A 10,000N car lifted by a ramp up to a height of 50cm, 3.A 70kg person lifted up 50m by a ski lift. How much GPE have the following objects lost?: 1.A 2N football dropping out of the air after being kicked up 30m, 2.A 0.5N egg falling 10m out of a bird nest, 3.A 10,000N car falling off its 50cm ramp. 4.Mr Richards when bungi-jumping off a 110-metre high bridge in Zambia in August

Don’t forget! Test! Use the revision sheet to help you study! Test on Thursday 26th January

Energy Circus Around the room are a few examples of energy changes (some simple, some a little more complicated!) For each example I want you to write the name of the experiment and then the energy flow diagram for that experiment You will have 2 minutes on each example.

Ready?

Go!

Sankey Diagram A Sankey diagram helps to show how much light and heat energy is produced

Sankey Diagram The thickness of each arrow is drawn to scale to show the amount of energy

Sankey Diagram Notice that the total amount of energy before is equal to the total amount of energy after (conservation of energy)

Efficiency Although the total energy out is the same, not all of it is useful.

Efficiency Efficiency is defined as Efficiency (%) = useful energy outputx 100 total energy input

Efficiency Efficiency is defined as Efficiency (%) = useful energy outputx 100 total energy input Can you copy this (with title) please?

Example Efficiency = 75 x 100 = 15% 500

Energy efficient light bulb Efficiency = 75 x 100 = 75% 100

Energy efficient light bulb Efficiency = 75 x 100 = 75% 100 That’s much better!

More complex examples

Let’s try some questions! Stick the sheet into your books and answer the questions