All atoms are made up of three different kinds of sub-atomic particles
- Electrons
- Protons
- Neutrons
Protons and electrons
Carry charges of the same magnitude but opposite sign
Excess of electrons
Negatively charged object
Deficiency of electrons
Positively charged object
Mass becomes charged by
- Loss/gain of electrons (electrons can be transferred from one object to another but protons are fixed in nucleus).
- Only electrons move, protons and neutrons cannot move
Different charges
Attract/pull towards each other
Similar charges
Repel/push away from each other
Insulators
Will retain charge for some time (longer if air is dry)
Conductors
Will not retain charge and it’s “leaks” away very quickly
Different Methods of charging objects
- Charge by friction
- Charge by induction
- Charge by contact
Charging by friction
Achieved by rubbing 2 materials against each other, causing transfer of electrons
Charging by induction
Object is charged by another object without touching the object
Charging by contact
Neutral object becomes charged due to being placed in contact with an object that is charged
What determines whether an object becomes negatively or positively charged
Triboelectric series ranks materials in the approximate order of their positive or negative charging tendencies
Electroscope
- Can be uncharged/charged
- Uncharged: leaf hangs against plate
- Charged: leaf gets like charge and repelled
How to discharge an electroscope
- Touch metal ball/knob with finger. Excess electrons will flow back into your body and electroscope will be neutralised
- Positively charged electroscope, it attracts electrons from conducting material (your body) from the ground, positive charge is neutralised
Law of Conservation of Charge
Charge can neither be created nor destroyed. It can only be transferred from one body to another
The number of electrons lost…
Are equal to the number of electrons gained by the other
When two identical charged objects touch one another
Charges move around and redistribute themselves evenly over both objects
Electric field represented using
Field lines
Properties of field lines
- Electric field lines never touch
- Direction of a field at a point
- Field lines closer together implies stronger field
Uses of electrostatics
- Photocopiers and laser printers
- Defibrillators
- Dust precipitators/electric smoke precipitator
- Paint spraying
- Insecticide sprays
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Definitions122
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Scientific Skills27
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Vectors10
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Graphs Of Motion5
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Equations Of Motion3
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Polyatomic Ions24
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Energy8
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The Atom35
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Quantitive Chemistry4
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Physical And Chemical Change22
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Kinetic Molecular Theory11
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Matter And Materials6
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Trends In The Periodic Table15
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Chemical Bonding17
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Intermolecular Forces21
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Solids16
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Electrostatics22
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Electric Circuits4
