Storing energy Introduce yourself as the facilitator and outline (briefly) your STEM background. Ask STEM Ambassadors (if present) to (briefly) introduce themselves and to say which STEM discipline/industry they are from.

Batteries and storage What is a battery? The dictionary definition is: a device containing one or more electrical cells. One thing that is really annoying is when batteries run out. What do they exactly run out of? How do they power things and how does the energy get there in the first place? Sometimes you need more than one battery to make a device work – how do we achieve this? Why are some batteries rechargeable and some not? There are lots of questions that we very rarely ask about batteries which is surprising as batteries serve a crucial purpose in modern life. What is a battery? The dictionary definition is: a device containing one or more electrical cells. So what is an electrical cell? The free dictionary definition is: A device, such as a battery, that is capable of changing some form of energy, such as chemical energy or radiant energy, into electricity.

How a battery works So we now know that a battery is a device that can change chemical or radiant energy into electricity. Let’s look at a typical battery to see how this is done. To store energy batteries are ‘charged’ which essentially involves creating an imbalance of electrons between the positive anode and negative cathode. The electrons stored at the anode side of the battery want to flow so that the chemicals in the battery are electrically balanced but cannot do this without a conductive circuit being completed between the negative and positive terminals on the outside of the battery. Connecting the circuit allows the electrons to flow and enables the stored (potential) energy in the battery to be converted to other forms of energy (e.g. a lamp) along the circuit. The difference in number of electrons between the positive and negative terminals of a battery (potential energy) is measured in Volts and we use the V symbol to reflect this. The rate of flow of electrons around a circuit is called the current. Current is measured in units called Amperes (Amps for short) and we use the A symbol to reflect this. Current flows through materials that conduct electricity (e.g. copper wire). Conductivity of a material is referred to as resistance and we measure resistance in Ohms using the Ω symbol. The power delivered by an electrical circuit is described in Watts (W).

Relationship between potential energy, power and current

Which battery holds the most potential energy? The 9volt battery holds the most potential energy.

Conductors and insulators Using the examples provided work out which materials are insulators and which are conductors: String? Plastic? Wood? Copper wire? Different materials have different resistances: an electrical conductor has a low resistance an electrical insulator has a high resistance You can easily find out which materials are conductors and which are insulators using a simple circuit. You set up a series circuit with a cell, lamp and wires. Leave a gap in the circuit between two of the wires. Then connect the two wires using pieces of each material and see if the lamp lights up: it will light up if the material is a conductor it will not light up if the material is an insulator 1 piece of string for each group (insulator) 1 piece of plastic for each group (insulator) 1 piece of wood for each group (insulator) 1 short length of copper wire for each group (conductor)

Making power go further To either get more power or prolong the time that they can deliver power, batteries can be connected together in different ways. We refer to these ways as in series and in parallel. Batteries connected in series increase the amount of potential energy available to power a device. In the examples here the positive terminal of one 1.5 V battery is connected to the negative terminal of the other 1.5 V battery to give additional V of potential energy. Look at the examples here, what amount of potential energy would each one offer if batteries were inserted? A=1.5, B=12, C=6. B C A

Different power for different needs Batteries connected in parallel offer longer lasting power but no increase in potential energy. To connect batteries in parallel the negative terminal of one battery is connected to the negative terminal of the other and the positive terminals are connected in a similar way. Using in parallel connection increases the current (A).   Which of the following applications would most suit in series or in parallel connection? Motors on a radio controlled car, a nightlight, an Ipad or tablet device.

Make your own electricity! 1. Wind the wire around your paper tube (about 20 times). 2. Connect both ends of the wire to the meter. 3. Take the a bar magnet and move it near the coil but not through it. Observe the meter. 4. Move the magnet in various directions around the coil. 5. Move the magnet through the coil, move the magnet at different speeds. Try moving the coil over the magnet. Make notes of your results. Work in your groups (3-4 pupils) to make electricity from a magnet. Seek answers and comments on what works best and produces the most electricity.

RAF examples: stored energy in action There are other ways to ’store’ energy and the RAF put some of them to good use! Take the example of a glider. It takes the energy created from warm air currents to create lift (as shown in the diagram). Once this lift has been utilised it converts that captured energy to create flight!