2.10 Producing electrical energies: batteries

10 April 2023

DC versus AC

• A direct current (DC) is one which goes around and around in the same direction – it is delivered from a battery

• An alternating current (AC) is one which goes back and forth over and over again – this is what we get from the mains supply

• If you look at a battery you will see two terminals

• One is a +ve called the anode

• The other is –ve called cathode

Examples of different types of batteries and where we use them

Appliance Battery material Battery type

Mobile phone Lithium ion Rechargeable

Modern car Lithium acid Rechargeable

Very old car Lead acid Rechargeable

Laptop Lithium ion Rechargeable

Television remote control Alkaline Non-Rechargeable

Watch Lithium iodide Non-Rechargeable

Non-rechargeable batteries

• A battery is made of a number of cells

• AAA is a 1.5 V cell, a PP3 is a nine volt battery

The dry cell

How do they work?

• When the two poles are connected the electrons can flow

• As the chemicals are used up fewer electrons are made so the battery is used up

• A chemical reaction occurs between the electrolyte and the anode which produces electrons

• The salt bridge is in the way so they cannot flow• These electrons flow to the cathode where there

are few electrons but…

How do they work?

1. A chemical reaction occurs between the electrolyte and the anode which produces electrons

2. These electrons flow to the cathode where there are few electrons but

3. The salt bridge is in the way so they cannot flow

4. When the two poles are connected the electrons can flow

5. As the chemicals are used up fewer electrons are made so the battery is used up

Why do we use them?

• Little current (like remote controls)

• Rarely used items (torches)

• They are cheap• Stay charged for

longer• …bad for the

environment!

Rechargeable batteries

• Cells in rechargeable batteries are called secondary cells

• These are mostly used in portable items that are used regularly, such as mobile phones and computers

• The chemical is used up as the battery is used but the process is reversible by applying an electrical current

Safety hazards

• Dead batteries must be disposed of safely

• Some batteries contain toxic mercury that may leak into the environment

• Leaking batteries may also cause burns if the acid comes into contact with the skin

• In some areas of the UK, all types of battery can be recycled

Questions

• Explain the difference between a rechargeable and a non-rechargeable battery. Give five examples of each

• Draw a labelled diagram of a primary cell

• Discuss with a partner the advantages and disadvantages of rechargeable and non-rechargeable batteries