4.5Chapter 4: Electricity

Dangers of electricity — Alhussan Physics - Stage 7 Revision Notes & Topical Questions

5 min read 7 parts Lesson 5 of 6 2 quizzes

📚 Alhussan Physics - Stage 7 Hub / Topical Revision

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4.5 Dangers of electricity — Fuses, Insulation and Electrical Safety — Alhussan International Academy — Physics (Stages 7–9) notes: Describe how electricity can be dangerous and explain how the risk of damage or injury can be reduced.Spark = charge moving through the air, heating…

Thundercloud
Lightning strike
Useful current
Static shocks
Lightning conductor
Refuelling cars and planes

Section 1 of 7Sparks and lightning

Spark

Spark charge moving through the air, heating it up.

We see light and hear a sound, and the moving charge is an electric current.

Air

Air it does not usually allow a current to flow, but a big difference in charge can make the air conduct electricity.

Lightning

Lightning it is an example of an electrostatic phenomenon, and there are lightning storms all over the world every day.

Thundercloud

Thundercloud the air moves around inside the cloud like rubbing a rod with a cloth.
This forms a region that is positively charged and a region that is negatively charged.
Negative charges at the bottom of the cloud can make a huge spark as they travel to Earth, which we see as lightning.
Sometimes a spark is produced between positive and negative regions inside the cloud.

Section 2 of 7Electric shocks

Lightning strike

Lightning strike if lightning strikes a person it can break bones, cause burns or even kill them.
The charge travels through the person to earth, and the current can damage the heart or stop it beating.

Useful current

Useful current doctors use an electric current to try to restart a patient's heart if it stops beating,
which can save lives.
- (a defibrillator uses charge to do this)

Static shocks

Static shocks people sometimes feel a small shock when they touch a car door, because the car has become charged by friction as it moves along.
You may hear sparks crackle as you remove clothing, or feel a shock from a door handle.
A student charged by walking across a carpet gets a shock from a metal handle because charge flows to it.
She would not get a shock from a plastic handle, because plastic is an insulator and charge cannot flow through it.

Section 3 of 7Risk and earthing

Risk

Risk the probability of something happening combined with the consequence if it did.

We cannot change the probability of lightning hitting a building, but we can change what happens if it does.

Earthing

Earthing connecting an object to the ground with a conductor so that charge flows away safely and the risk of damage by an electric current is reduced.

Lightning conductor

Lightning conductor a thick strip of metal such as copper running from the top of a tall building down the wall to a copper plate buried underground.
If lightning strikes, electrons flow down the strip into the ground, because metal conducts much better than the building.

Section 4 of 7Earthing in other situations

1Refuelling cars and planes

Refuelling cars and planes friction of fuel moving along the pipe can cause charge to build up, and a spark could make the fuel catch fire.
Fuel pipes are earthed by attaching a metal wire, so any charge flows down the wire to earth.

2Electronics

Electronics engineers who make circuits for TVs or phones wear wristbands connected to a metal wire that goes to the ground.
Any build-up of charge flows down the wire to earth rather than through the delicate components.

Section 5 of 7Safety in mains circuits

Insulation

Insulation appliance wires are covered in insulation to prevent electric shocks.

Fuse

Fuse a safety device containing a thin wire in a circuit that melts if too much current flows, breaking the circuit and preventing overheating and fires.

Earth wire

Earth wire it gives an escape route for current if a fault occurs.

Section 6 of 7Key terms

Term	Meaning
Electrostatic phenomenon	an observable effect caused by static electric charge, such as lightning.
Earthing	connecting an object to the ground with a conductor so that charge flows away.
Lightning conductor	a metal strip from the top of a building to the ground that carries lightning current safely.
Risk	the probability of something happening combined with its consequence.
Fuse	a safety device containing a thin wire that melts when the current is too large.
Spark	charge moving through air, heating it.