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Friction, Conduction and Induction

Friction, Conduction and Induction. How do you charge an object?. There are three ways to charge an object: 1. Charge by Friction 2. Charge by Conduction 3. Charge by Induction. How do you measure “charge”.

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Friction, Conduction and Induction

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  1. Friction, Conduction and Induction

  2. How do you charge an object? • There are three ways to charge an object: 1. Charge by Friction 2. Charge by Conduction 3. Charge by Induction

  3. How do you measure “charge” • The unit of measure for electrical charge is the Coulomb (C). In equations it is symbolized by a “q” • Eg: q = 900C • One Coulomb is equal to the charge of 6.25 X 1018 electrons (-) or protons (+). • That is to say, one Coulomb has 6.25 X 1018 electrons.

  4. Charging Objects • Most objects start out electrically neutral, but by CHARGING an object you create an imbalance in the number of electrons and protons; the object is then charged and is either positive or negative. • You can charge an object through: • Friction – the transfer of electrons from one object to the other • Conduction – by having two objects TOUCH each other and transfer electrons from one object to the next. • Induction – By inducing electrons to move from one object to the other.

  5. Charging by Friction • When two neutral objects are rubbed against each other, one object may pull electrons away from the other creating one positive object and one negative object.

  6. Electrostatic Series: • All objects begin neutral & can become positively or negatively charged • A positively charged object has more positives than negatives • A negatively charged object has more negatives than positives

  7. Electrostatic Series: • Electrostatic seriesis a list that ranks objects’ ability to take negative charges Rubber Items at top take negatives Ebonite Polyethylene Cotton Silk Wool Items at bottom lose negatives Glass Acetate Fur / Hair

  8. Items at top take negatives Ex #1 Your cat rubs against a rubber balloon. What will be the charge on the balloon? Your cat’s fur? Rubber balloon becomes negative Rubber Rubber Ebonite Polyethylene Cotton Silk Wool Glass Acetate Fur / Hair Cat’s fur becomes positive Fur / Hair Negatives

  9. Items at top take negatives Ex #2 In a lab, you take a piece of neutral wool & neutral polyethylene & rub them together. What will be their charges? Polyethylene balloon becomes negative Rubber Ebonite Polyethylene Cotton Silk Wool Glass Acetate Fur / Hair Polyethylene Negatives Wool Wool becomes positive

  10. Ex #3 In a lab, you rub a piece of cotton & ebonite together. Then you rub a piece of silk & wool together. You then bring the charged piece of cotton& the charged piece ofsilktogether. What will happen? Rubber Ebonite Polyethylene Cotton Silk Wool Glass Acetate Fur / Hair - Cotton is + Silk is - + - They wouldATTRACT +

  11. Ex #4 You rub your hair with a balloon. Explain using words & pictures, why your hair “sticks up”. 1st Hair & balloon are both neutral _ + _ _ + + 2nd Rubber balloon takes negative charges from the hair. So, balloon becomes negatively charged & hair becomes positively charged + _ + _ 3rd Since hair is positive & like charges repel, hair sticks up!!!

  12. Charging by Conduction • An object can be charged by touching it with another object that already has a charge. The resulting object will then have the same charge but weaker in strength than the original object.

  13. Charging by Conduction • This image shows how a positive charged object alters the charge on the globe via conduction.

  14. Charging by Conduction • This image shows how a negative charged object alters the charge on the globe via conduction

  15. Charging by Induction • Objects do not touch (one is charged, one is neutral) • Proximity of the charged object causes (induces) the charges in the neutral object to separate.

  16. Charging by Induction • This image shows how a negative charged object alters the charge on the globe via induction.

  17. Charging by Induction • This image shows how a positive charged object alters the charge on the globe via induction.

  18. Key Points to Remember • Two types of charges – positive(+) & negative (-) • “Opposites Attract” • “Like Repel” • Items at the top of the electrostatic series list take negative charges • Only negative charges move • Three methods to charge an object: friction, conduction, induction. These three methods are what cause static electricity.

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