Static Electricity

# Static Electricity

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## Static Electricity

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1. Static Electricity

2. Introduction positively The force of electrical charges can be quantified in several different ways. Most atoms are neutral due to an equal number of protons and electrons. Only electrons can leave an atom. When electrons leave the atoms of an object the object becomes charged. When the atoms of an object gain electrons the object becomes charged. If a balloon is rubbed against a surface such as a person’s hair, the between the two objects may cause to leave one surface (the hair) and be deposited onto the other (the balloon). These particles on the balloon remain here as electricity until they are released as discharge. negatively friction electrons static static

3. Think it Over 1. How did you get the can to move? Be specific. • After rubbing the balloon on someone’s head the balloon is brought close to the can. When this happened the can rolled toward the balloon.

4. Think it Over 2. Why do you think the can moved? • Electrons were transferred from your hair or shirt to the balloon. The balloon became negatively charged. When it came close to the can the negatively charged balloon and pushed away the electrons in the can because like charges repel - the balloon induced a positive charge on the can. The positively charged side of the can was then attracted to the negatively charged side of the balloon.

5. Think it Over 3. What did you learn about electricity from this activity? • Electricity can cause objects to move – so it’s a force! • Static electricity can be caused by friction. • Objects do not need to be touching in order for charges to build • Opposite charges attract

6. Charged Particles http://www.geocities.com/CapeCanaveral/Hall/1410/charges.gif Electricity is based on moving charged particles. Positively charged Protons Negatively charged Electrons Unlike charges = attract Like charges = repel Fun Interesting Fact: Ben Franklin gave names positive and negative to the charges!

7. Differences Between Magnetic Poles and Electric Charges Different Magnetic poles = always in pairs Electric charges = can be alone Same two ends (pos/neg; north/south), field around them, like repel, opposite attract

8. Electric Force and Field Electric Force: attraction/repulsion between charges Electric Field: Area around a charged object where the electric force is exerted

9. Field Lines Lines show direction and strength of field Point away from positive charge and towards negative charge Field is strongest closer to the charge Closer together lines…stronger the electric field http://www.rwc.uc.edu/koehler/biophys.2ed/images/fields2.gif

10. Field Lines Attracting Repelling

11. Static Electricity Static = stationary (not moving) Temporary partial charge Charges build up – do not continue to flow http://www.esdsystems.com/images/carpet.gif

12. Transferring Charge Conservation of Charges: charges are not created or destroyed; charges are transferred (if one object loses electrons, another gains them)

13. Transferring Charge Electrons Transfer by: Friction – rubbing of uncharged objects (example: socks on carpet) Conduction – touching of a charged object to another object (example: charged sock causes charged foot) Induction – no touching of objects, caused by electric field of one charged object attracting or repelling electrons from another object (charge from finger can cause charge on doorknob without touching it)

14. Friction and Induction

15. Giving Up Electrons NO!! Not all atoms in a substance will give up electrons. Not all electrons will leave the atoms either www.school-for-champions.com

16. Visibility Charges cannot be seen However the charges can be detected by an electroscope

17. Static Discharge • Static Discharge: loss of static electricity • When + and – objects are brought close together electrons will transfer from one object to the other until there are equal charges on both objects • Can cause a spark – the transferring electrons heats the air until it glows http://weathereye.kgan.com/cadet/lightning/electricity.html

18. Lightning • Lightning is static discharge! • Negatively charged cloud induces a positive charge on the ground and the lightning we see is the actually the path of electrons traveling through the air. http://ffden-2.phys.uaf.edu