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Why can you touch a battery but not an electric fence?

Why can you touch a battery but not an electric fence?

Electricity is a marvellous thing. Everyone knows that a loose electrical wire or the electric fence around a field can give you a shock. So best not to touch it. But if you grab hold of a home and garden variety battery, you feel ... nothing. Yet the battery will light up your flashlight or play your transistor radio. Why the difference? Get ready for a brief lesson in battery science! 

First of all: what is a battery?

A battery can best be described as a chemical energy source that produces a limited quantity of electrical energy wherever you need it. The electrical current that flows from the wall socket comes from an electrical plant. (Or from sustainable sources such as solar panels and windmills.) The energy from a battery is produced by the chemical substances inside the battery. And it does so until the battery is “dead”.  

What is in a battery?

Let’s take a look inside. Each battery consists of one or more cells. And each cell has four components:

  • two electrodes (conductors)
  • an electrolyte, a chemical substance between the electrodes
  • a separator between the positive and negative electrode that prevents internal short circuits.

They are housed in a metal or plastic casing. On the outside of the battery there are two terminals, indicated with a plus (the cathode) and a minus (the anode) sign.

Zaklamp batterijen

How exactly does a battery work?

When the two ends of the battery are connected in a circuit, such as in a flashlight, the battery is activated. Chemicals in the electrolyte are thereby converted into different ones. Ions are formed (these are atoms with too few or too many electrons) that help produce chemical reactions in the electrolyte. At the same time, electrons from the negative end flow towards the positive end of the outermost circuit. And the flashlight comes on!

This process continues until an equilibrium is reached between the elements of the - and the + ends. The ions then stop moving through the electrolyte and the electrons stop flowing. The battery is now discarded.

How does that work with a rechargeable battery? With that type of battery, the chemical processes are reversible. By creating electrical tension, you can force the electrons to flow in the opposite direction and reverse the chemical reactions. In sum: you store new energy.

Now hold a fully charged battery in your hand ...

Put one finger on the positive end and one finger on the negative end. Do you feel anything?

Maybe not. But did you pay careful attention to what you feel? If you hold on to both ends of a battery (positive and negative), a small amount of current runs through your body.

Batterijen vastpakken

But the electricity is very weak (much weaker than the current from the electrical network) and also: there are no metal conductors in your body. The bigger the battery, the greater the chance that you will feel something. If you wet your hand, that can intensify the effect, as well, and you may feel the current (slightly) tingle. Try this only with small alkaline (AA or AAA) batteries, for while electricity is marvellous, it is not a toy. Keep safe!

Afplakken 9V batterij

Do you know me?

I am often found in smoke detectors and am often used in experiments at school.

Safety tip: It is best to cover my two poles with a piece of sticky tape to prevent short circuits.

Batteries come in many different forms.
Learn more about batteries!

Preventing short circuits

A battery will not give you any shocks. But however, a short circuit can occur.

Remember: in a battery, electricity flows from the negative end to the positive end. If the positive and negative ends of a battery come into direct contact with each other, a short circuit occurs. Result: the battery will drain very quickly. Very rarely, a sudden release of energy can cause a sudden burst of heat. With all the harmful consequences thereof.

Tip: for some batteries (e.g. 4.5 and 9 volt batteries and button cells), it’s a good idea to cover the terminals with a piece of sticky tape before you bring them to the Bebat collection point.

Extra fact: did you know that the “label” on the battery not only provides information but also prevents short circuits? It leaves exposed only the bits on the positive and negative end needed to generate electricity, and protects the rest of the battery from a short circuit. So never peel the label off a battery. Has it come off? In that case, put the battery in a plastic bag and bring it as soon as possible to a Bebat collection point.

Proper handling of batteries?

Discover all our safety tips.

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