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Electricity

Electricity. The shocking introduction. Electrical charges. Everything in the universe is made up of atoms Those atoms are made up of subatomic particles Three main ones: Neutrons Protons Electrons. Electric Charges continued. Neutrons have no electric charge

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Electricity

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  1. Electricity The shocking introduction

  2. Electrical charges • Everything in the universe is made up of atoms • Those atoms are made up of subatomic particles • Three main ones: • Neutrons • Protons • Electrons

  3. Electric Charges continued • Neutrons have no electric charge • Protons have positive electric charge • Electrons have negative electric charge • Even though protons are much larger than electrons, their charge is exactly EQUAL AND OPPOSITE.

  4. Moving charges • Whenever charges move around (from current in a wire to lightning strikes), it is always ELECTRONS that move. • That’s pretty much it for this slide.

  5. Attraction and Repulsion • Like charges repel • Unlike charges attract • Draw on the situations below to show which are positive and which are negative charges.

  6. Charges and neutrality • Pretty much anything that you’ll come across starts off electrically neutral. • This is why you don’t shock yourself when you touch stuff in your daily life. • Sometimes, objects acquire excess electrons. These objects then become NEGATIVELY charged. • Other times, objects lose electrons. These objects then become Positively charged.

  7. Charge imbalances • If something has a charge imbalance, that means that it has more/less charge than usual. • If two objects with UNLIKE amounts of charge come into contact, charge will move from one to the other until they are equal. • What kind of charges move?

  8. Conductors and Insulators • Just like for heat, some materials are good electrical conductors and some are good electrical insulators. • Usually, the same materials are good conductors of heat and electricity, for the same reason. • Electrons in conductors are not held tightly to their atoms, so they can wander off • Let’s look at a picture:

  9. Conduction of Electricity http://thephysicstutor.com/notes/images/conduction.png

  10. Conductors • An important thing about conductors: • Any extra charge is on the outside • A solid conductor won’t have any charge in the middle • The reason for this is that the charges all want to get away from themselves as much as they can.

  11. Zapping stuff • So, let’s say you acquire an excess of electrons (like, say, by shuffling your feet across a carpet). • You now have a negative charge. • Your younger brother/sister has a neutral charge. • When you sneak up behind them and touch their ear, what happens? Why? • Try this at home!

  12. Electric Force • All charges exert forces on all other charges. • Like charges push each other away • Unlike charges attract each other. • The magnitude of the force depends on the amounts of charge and the distance between them. • However, a charged object can exert a force on something that is neutrally charged. Why?

  13. Force between charged object and neutral object • Let’s say you have a negatively charged object (left) that is brought near a neutrally charged object (center). • The negative charge in the first object repels the negative charge on the second object to the other side, leaving the closer side with a positive charge. • So they will attract, even though the second one was initially neutral. - • + • - - - • - + - • + • - • + - - • - • + - • + - • - • - - • - • - - - - - • - • + - • + • + • - • - • - • - • - • + • - - • + • - • + • - • + • - • - - • - • + • +

  14. Charging by Induction http://etudeallegro.com/tuition/images/stories/POL/induction-charging-all-steps.jpg

  15. Charge Polarization • Look at page 512 in your book • In insulators, charges can’t move around like they can in conductors. • However, they still TRY to rearrange themselves. • So even insulators can experience electrical forces.

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