Electric charge

What happens when an acetate or perspex rod is rubbed with a woollen duster?

-A static charge is caused by friction. -ELECTRONS from acetate rod rubbed onto duster. -Acetate rod LOSES electrons (fewer electrons than protons= overall charge POSITIVE) -Duster Gains electrons(more electrons than protons =overall charge is NEGATIVE ) Tip; Perspex gives a POSITIVE PERSPEctive on life ; An A Grade (Acetate) is a POSITIVE thing

What are the advantages of electrostatic spray painting?

1. Less waste as charged paint particles attracted to opposite charge of metal object so less falls on floor. 2 Can spray awkward corners as like charged paint particles on the object will repel each other and will spread out to form an even coating and round awkward corners

What are the hazards of static electricity?

1. Lightning causing death, burns and fires 2. Refuelling e.g. aircraft and petrol stations explosions 3. Electric shocks and sparks

What are the disadvantages of static?

1. attracts dust to computer and tv screens 2. causes clothes to stick together after being in tumble drier 3. statin may cause sparks that can cause fire 4. large charges can cause electric shocks and death

Describe an experiment to show like unlike charges attract using FRICTION ?

As before eg rub 2 rods with same Woollen cloth and suspend by insulating thread from clamp and bring one rod close to but not touching the second rod BUT use one acetate or Perspex (becomes positive) and one polythene rod (becomes negative)

How can people avoid electric shocks in thunderstorms?

Avoid trees which are more likely to be struck by lightning Avoid metal e.g. umbrellas which would conduct the lightning

What causes a negative charge?

Gain of electrons (overall number of electrons in a material is greater than the number of protons so the overall charge is negative) TIPS: POLYTHENE (plastic bags) are negative Nit (plastic) Combs are Negative Naughty Negative balloons after rubbing on hair

Does attraction prove that materials are oppositely charged?

No as although unlike charges attract- attraction can also occur between a charged and an UNcharged material eg the comb and paper The only true test of a charged material is if it REPELS another material of the same charge

What 3 methods can cause a static charge to build up?

1. FRICTION eg rubbing 2. INDUCTION eg close but not touching 3. CONDUCTION eg touching Tip; F IN C

What happens when a polythene rod is rubbed with a woollen duster?

-A static charge is caused by friction. -ELECTRONS from duster rubbed onto polythene rod. -Polythene rod gains electrons (more electrons than protons= overall charge NEGATIVE) -Duster loses electrons (fewer electrons than protons= overall charge POSITIVE) Tip; polythene (plastic) carrier bags are a negative thing for the environment -When drawing -the overall charge must be conserved so just move electrons don't add new ones.

Describe an experiment to show like charges repel using FRICTION ?

-Rub two Rods of the same insulator material eg an acetate (or Perspex) with the same cloth eg a wooden duster -Suspend one rod from a clamp using an insulating thread (so charge cannot flow away) and bring the second rod close to but not touching -The two rods will repel each other as like charges repel As before electrons move from acetate or perspex to cloth... 2 rods will have the SAME POSITIVE charge so will repel each other Note; if 2 rods of polythene are used instead they will also REPEL each other but the Polythene rods become NEGATIVELY charged by the cloth

How does a van de Graaf generator work?

Bottom metal comb is positively charged by power supply Removes electrons from insulating belt Positively charged insulating belt is moved upwards towards dome by rollers In hollow metal dome electrons move via metal comb to positively charged belt so surface of dome becomes postively charged and descending belt becomes negatively charged BIGGER CHARGE - BIGGER BALL and FURTHER FROM GROUND

What happens after you comb you hair on a dry day with a plastic comb?

Electrons move from the HAIR to the COMB. The COMB becomes NEGATIVELY charged (as it has more electrons than protons in the comb) The HAIR becomes POSITIVELY charged and the same positive charge on the each hair will repel each other as like charges repel and the hair will becomes "fly away" Note; the total charge must be conserved so the overall positive charge on the hair equals the overall negative charge on the comb and the hair cannot remain neutral Tip; hair becomes positive -comb and balloon negative

How does a photocopier work?

Drum is positively charged until light falls on it Charge is lost in the area where light hits it Black toner sticks to the drum where there is still charge Paper is heated to stick the toner to it

What materials enable the build up of static charge?

Insulators (And on a conductor if the path of flow of charge is prevented by an insulator)

What causes a positive charge?

Loss of electrons -overall number of electrons on a material is less than the number of protons so the overall charge is positive Eg Acetate Rod- An A (ACETATE) rod is positive Perspex rod - PERSPEXtive is a positive Hair- eg Ponytail positive after combed with a plastic comb

What are 4 uses of static electricity?

Photocopier inkjet printer electrostatic paint spraying

What is static electricity?

Static electricity= build up of ELECTRIC CHARGE caused by the TRANSFER of ELECTRONS and when the charge is not then FREE to FLOW (hence static)

How can a balloon stick to a wall after rubbing it on your head?

The hair LOSES electrons to the ballon and becomes POSITIVELY charged as a result of the friction. The ballon becomes NEGATIVELY charged as it gains electrons The neutrally charged wall becomes charged by INDUCTION and becomes POLARISED as electrons will be repelled from the surface by the negatively charged ballon (like charges repel) which will then be attracted to the opposite positive charge on the wall. Eventually the balloon will fall off when the negative electrons leak off the balloon and there is no longer a force of attraction. This is why is it only a temporary effect.

How can static be reduced?

The object should be earthed so the charge can flow away and not build up eg Lightning conductor rods on churches

What happens to the students hair who touches the Van de Graaf dome and why? What conditions does this need to work?

The positive electric charge is transferred from the dome to the hair follicles which then have the SAME positive electric charge so will REPEL each other which is why the hair stands up. Conditions needed: Student must stand on an insulator or carpet so charge cannot flow away Hair must be dry as less charge builds up in humid or moist weather

Why does a comb initially attract pieces of paper then repel them after touching the paper?

This is an example of CONDUCTION.

What is an insulator?

a material that DOES NOT CONDUCT charge Eg non-metals e.g. wool, glass, acetate, Perspex, polythene

What happens if after combing your hair, the plastic comb is brought close to pieces of paper and why?

Uncharged pieces of paper= attracted to the negatively charged comb. CHARGING BY INDUCTION = comb does not need to touch the paper The paper becomes POLARISED e.g. whilst overall neutral charge in paper, the electrons are repelled by the comb's negative charge and move away. The protons within the paper are attracted to the comb's negative charge and move towards that surface of the paper and the paper is therefore attracted to the negatively charged comb The overall electric charge of the paper remains neutral This demonstrates that electric charge is a non contact force

What is a conductor?

a material that does conduct charge Eg metals - copper, silver some non metals e.g. graphite (carbon)