Before the lesson, arrange the devices throughout the classroom so that the students can walk around to visit each. Add a visible card next to each, so that they can find each device or item. Ideally the devices are functional e.g. the fan is blowing, the light bulb is on, the speaker is playing music.
Review types of energy with students:
gravitational potential energy is the energy stored in an object when it is high
kinetic energy (also called motion or mechanical energy) is the energy something has when it is moving
heat (thermal energy) is the energy in something warm
sound energy we can hear as noises
light energy is the energy in light emitted from an object
nuclear energy is the energy contained in an atom
electrical energy is the energy carried by electricity
chemical energy is the energy contained in the chemistry (i.e. the molecules) of an object or living thing, often created and released through chemical reactions
magnetic energy is the energy contained in magnetic materials
elastic potential energy is the energy stored in something that is stretched (before it returns to its unstretched state)
Students visit each device and record on their worksheet the type of energy they think makes the device work (i.e. the input energy) and what kind of energy it produces (i.e. the output energy). They draw a line from an energy input type on the left to energy output type on the right, then write the name of the device/object on the line. There may be more than one kind of energy produced by a device, and more than one kind of energy may make a device function. They may not use all the energy types on their worksheet. Try and focus students on the input energy that is the last energy to enter the device, and the output energy that the device is intended to produce. They can make notes on other kinds of energy that are unintended output energies (often heat and sound).
Discuss their results.
There are often no wrong answers, as students will see many of the ways that devices function. Students may also make educated guesses as to how devices work (e.g. is there a magnet it there that makes it work?) - encourage discussion around these ideas.
List of devices/objects with likely energy inputs and outputs:
fan: electrical in, motion (of the air molecules) out
light bulb: electrical in, light out. heat is often also an output energy of lightbulbs, so making them less efficient
speaker: electrical in, sound out
kettle: electrical in, heat out (also sound out)
telephone: sound in (also motion in as you dial the number), electrical out
battery: chemical in, electrical out
candle: chemical in, light (and heat) out
magnetic stripe card: magnetic in (of the encoded magnetic pattern in the stripe), also motion in as you swipe it, electrical out (as the card communicates with the card reader)
ukulele (or other stringed instrument): elastic potential energy (of the stretched string) and motion energy (of the hand strumming) in, sound out
elevator: electrical in, gravitational potential and motion energy out
plant:light (of the sun) and chemical (of the minerals and water) in, chemical out (as the plant grows by building up chemical structures)
Discussion around electrical energy production and renewable energy
Students may notice that many of the devices require electricity as an energy input. This can lead to discussion around how we produce electricity.
- Fossil fuels (coal, oil, natural gas) are used extensively for energy production. The fuel is burned to make heat, which is used to boil water and make steam (chemical energy to heat energy to motion energy). The steam is channeled over turbines, which turn with the movement of the steam (motion energy). Turbines are connected to generators to make electricity (motion energy to electrical energy). When the fuels are burned they produce carbon dioxide, which is a greenhouse gas, so contributing to global warming.
- Nuclear power uses the energy contained in a uranium atom. Uranium atoms are split to make heat. The heat is used to heat water and make steam which flows over turbines which powers generators to make electricity. Nuclear power stations can be built safely, but the nuclear waste from this kind of energy production is a problem.
Optional: to help understand how generators work, demonstrate a motor. A motor is a wire with a current through it next to a magnet, and the forces combine to make the wire move. A generator is the reverse: a wire made to move next to a magnet produces a current in it, which is electricity.
Renewable energy sources are becoming more common, with the urgency to curtail global warming.
- Solar power is the conversion of light to electrical energy. Photovoltaic (PV) cells make up solar panels which convert light directly to electricity. Concentrated solar power (CSP) concentrates sunlight to make enough heat to drive a steam turbine and electricity generator.
- Hydroelectric power uses the gravitational potential energy of water behind a dam to drive turbines as it falls, which are hooked to generators. This is the most common renewable energy. Dams can be negative in that they flood whole ecosystems and maybe human communities, but they can also be positive in making a reservoir for areas that have long periods of drought.
- Wind energy uses the motion of wind to turn turbines, which are connected to generators.
- Geothermal energy uses the heat energy deep in the earth. Pipes running deep underground and up again (called geothermal heat pumps) can bring the heat to the surface, where it can be used directly to heat buildings. Alternatively, steam is either collected from underground, or made by injecting water into the warmth underground. Above ground, the steam drives turbines and generators. Iceland uses 90% geothermal heating.
- Wave energy uses the motion of the waves to drive turbines.
- Tidal energy uses the rising tide to fill a reservoir, from which water can later fall to drive a turbine.
- Biomass energy (or Bioenergy) is the method of burning organic matter to make heat for steam that drives steam turbines. Vegetable oil crops, algae, compost, mature, methane from cow farts are kinds of biomass used for this kind of energy production.
- Salt and temperature gradients in the ocean can be used for making energy