2.10 Producing electrical

energies: batteries

12 December, 2010

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