additional physics – forces l/o :- to know what happens when insulating materials become charged...

Additional Physics – Forces

L/O :- To know what happens when insulating materials become charged

Static Electricity

Exam Date -

http://www.youtube.com/watch?v=aO-phqmyqdY



1. Name the 3 sub atomic particles in the nuclear model of the atom?

2. Which of these particles can move to conduct heat or electricity?

3. How fast can electricity move?4. What electrical charge do protons

have?5. What colour are electrons?

• L/O :- To know what happens when insulating materials become charged

• What are the colours of the 3 main wires in a plug? Which one is which?

• How does a fuse work?• How does a circuit breaker protect the

electrics in your home?• What are the rules for current in – Series circuits?– Parallel circuits?

• L/O :- To know what happens when insulating materials become charged

(Is it the same down branches of a parallel circuit or does it split down branches of a parallel circuit?)

What causes lightening?

Movement of clouds (usually when a hot and cold cloud come together) causes one portion to become negatively charged and another to become positively charged. Eventually the charge builds up enough until it equalises itself - creating a spark - which is the lightening bolt.

Structure of the Atom

• Draw and label an atom. Add the electrical charges on each particle.

Quick questions: Charge on the Atom

1. What is the overall charge on an atom?

2. What happens to the charge if it loses electrons?

3. What happens to the charge if it gains electrons?

4. Which is the only type of charge/particle that can move?

Practical – making static charges move

• Rub 2 insulators together.

• Electrons move from one insulator (positively charged) to the other (negatively charged)

• There is an electrostatic force between charged objects.

• Same charges repel, opposite charges attract.

Practical – making static charges move

• Rubbing insulators together.

• Electrons move from one insulator to the other.

• This means 1 insulator gains electrons (becomes negatively charged)

• While the other loses electrons (so become positively charged)

Charging by Friction

• Some insulators become charged by rubbing them with a dry cloth.

• Experiment with the dusters and insulating rods.– What happens when you bring 2 charged rods

into contact with each other?– Charge up the rod and see if you can move/pick

up small scraps of paper.– Bring a charged rod near to a slow running flow

of water from a tap. What happens?– What happens if you do the same with a metal

rod?

Results

• You should have found that 2 objects with the same charge will repel each other

• 2 objects with different charges should attract each other

Like charges repel - Unlike charges attract

• You cannot charge a metal rod as it is a conductor and conducts the charge away to earth.

Practice Questions

Van de Graaff Generator

• Observe the Van de Graaff generator– How does it work?– Why does it make your

hair stand on end?– Why can it be

dangerous?!

*Do not go near if you have a pacemaker


• Sparks - connect the discharge wand to Earth and switch generator on (wait a few minutes and then bring wand close to dome to see sparks)


• Hair - have individual on insulating box and hold generator

• Why does your hair stand on end?


• Rice krispies – place (and stick) and small plastic bowl on the top of the generator and add some rice krispies

• Why do they erupt out of the bowl?!


• Flying saucers – place 10 metal saucers the top of the generator

• Why do fly off, one by one?


• What will happen to the fluorescent tube when it is placed on the Van de Graaff generator which has been on (for a short time)!


• The Van de Graaff generator has a dome which charges up when the generator is switched on (massive sparks can occur if the charge on the dome builds up too much)

The belt rubs against a felt pad, becoming charged

The belt carries the charge onto an insulated metal dome

Sparks are produced when the dome can no longer hold any more charge

Van de Graaff Hair: The charge transfers to the individual and hair

follicles get charged. The hair follicles then try to repel one another (which is why it stands on end)

Rice Krispies: The rice krispies all pick up the same charge from the generator and try to repel on another.

Flying Saucers:The top pan lifts off as it picks up the charge and is repelled, then next pan picks up charge and it is repelled etc…

Fluorescent Tube:Charge flows from the Van de Graaff generator through the tube and down to Earth, lighting it up (small charge and small enough voltage will still give a slight shock)!

What have you learnt?

• Can you explain how static electricity is caused?• What happens when you bring like charges together?• What happens when you being opposite charges together?• Why does touching the Van de Graaff make your hair stand on end?• What would happen if you were to touch a metallic object after the Van de Graaff?