Chapter 2.9 Electric charge - Summary Pearson Edexcel International GCSE (9-1) Physics Student Book - Physics

2 - 9 Electric charge
● Protons have charge +1, neutrons have no charge, electrons have charge
-1; number of protons = number of electrons, ∴ atom has no overall
charge (neutral)
● If number of protons ≠ number of electrons, atom called ion
● ***Number of electrons > number of protons, negative charge (gain of electrons);
Number of electrons < number of protons, positive charge (loss of electrons)



Conductors and insulators
● Conductors e.g.: metals, graphite
● Insulators e.g.: plastics, rubber, glass, wood



Forces between charges and static electricity
● Insulating materials can be charged by friction
● ***E.g.: rubbing uncharged plastic rod with uncharged cloth, electrons on surface of
rod transferred to surface of cloth (i.e.: ASSUME rod becomes positively charged,
cloth becomes negatively charged)
● ***Static electricity: imbalance of electric charges within/on surface of material
● ++/-- (like charges) repel (force of repulsion), +- (unlike charges) attract (force of
attraction)




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, Forces between charged and uncharged objects***
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