Charging by Contact 1 You can charge a

Charging by Contact 1. You can charge a neutral object by rubbing it with a different material (friction). 2. Sometimes, you can charge an object just by touching it with another object and then separating the two objects (conduction). • Electrons from one object move onto the other object. 11. 2

Charging by Contact: Friction 11. 2 neutral What is the charge on the hair? What is the charge on the comb? neutral

Charging by Contact: Friction 11. 2 After combing positive negative What is the charge on the hair? What is the charge on the comb? Why do the comb and hair attract? They are oppositely charged. How can we determine the charge that develops on each object?

Charging by Contact: Friction The electrostatic series helps you determine whether an object will become positively or negatively charged when it is rubbed with a different material. – For two materials, look at their positions in the electrostatic series. – The material closer to the top of the list will lose electrons and become positively charged. – The material near the bottom of the list will gain electrons and become negatively charged. 11. 2 electrostatic series

Handout: Charging Objects by FRICTION This method of charging objects involves rubbing two neutral objects together. The contact allows electrons to be transferred from one substance to ______ the other substance. One substance will gain negatively electrons (and become _______ charged) while the other will lose electrons (and become positively _______ charged). Since the two objects have attract opposite charges, they will _______ each other.

Handout: Charging Objects by FRICTION The various atoms that make up all substances have different forces of attraction for electrons. Some have a strong hold on electrons while others have a weak hold on electrons. A list showing the relative attraction of different substances for electrons is shown on the next handout. This list is called the Electrostatic Series ________________.

Handout: Charging Objects by FRICTION Example: A piece of fur is rubbed with an ebonite rod. What is the charge on each object and explain how the charge was produced? If we look to the Electrostatic Series, we see that the ebonite has a _______ hold for electrons than fur. stronger When the fur and ebonite are rubbed together, some electrons from the _____ move to the fur _______ because ebonite has the _______ ebonite stronger attraction for electrons. ebonite Since the _______ gains electrons, it becomes ________ charged. negatively Since the _______ loses electrons, it becomes fur ________ charged. positively

Handout: Charging Objects by FRICTION Example: If cat fur is rubbed with a glass rod; stronger The fur (having a ________ hold on electrons) gain will ______ electrons and become negatively ________ charged. weaker The glass (having a ________ hold on lose electrons) will ______ electrons and become positively ________ charged.

Charging by Contact: Conduction 11. 2 A neutral object can become charged if you touch it with a charged object. • If the charged object is negatively charged, electrons will move onto the neutral object. • If the charged object is positively charged, electrons from the neutral object will move onto the positively charged object. The negatively charged rod is moved toward a neutral pith ball electroscope so that both objects touch While the two objects are touching, some electrons from the rod move onto the pith ball

Charging by Contact: Conduction If two charged objects touch, electrons will move away from the object with more electrons until both objects have the same charge.

Handout: Charging Objects by CONDUCTION This method of charging objects involves contact between a charged object and a neutral object. Example #1: A negatively charged rod touches a neutral pith ball. The _______ on the negatively charged rod repel each other and jump from the _____ to the ________. The negative rod negative has shared its electrons with the pith neutral ball and they are now both ________ charged.

Handout: Charging Objects by CONDUCTION This method of charging objects involves contact between a charged object and a neutral object. Example #1: A negatively charged rod touches a neutral pith ball. e- electrons on the negatively The _______ charged rod repel each other and jump rod from the _____ to the pith ball ________. The negative rod negative has shared its electrons with the pith negative neutral ball and they are now both negatively ________ charged.

Handout: Charging Objects by CONDUCTION *** The neutral object gets the ______ charge as same the charged object since the charged object shares its charge with the neutral object.

Handout: Charging Objects by CONDUCTION Example #2: Show the charge distribution and the position of the leaves of the metal-leaf electroscope before and after being touched by a positively charged rod. Neutral Positive Before After

Handout: Charging Objects by CONDUCTION Example #2: Show the charge distribution and the position of the leaves of the metal-leaf electroscope before and after being touched by a positively charged rod. Neutral Positive Before After

Handout: Charging Objects by CONDUCTION When the positively charged object touches the neutral electrons electroscope, _______ jump from the electroscope rod _________ to the ______ (because of the attraction between electrons and protons). The positively electroscope is now __________ charged lost because it ______ electrons. Since it is charged, its repel / separate leaves will _________.

Handout: Charging by CONDUCTION Figure 1 e- e- Neg

Handout: Charging by CONDUCTION Figure 2 ee-

Handout: Charging by CONDUCTION Figure 2 ee- Pos

Grounding 11. 2 When a charged object touches a large neutral object such as Earth, the charged object becomes grounded and loses its net charge. – If the charged object was positively charged, electrons from the large neutral object move toward the charged object. – If the charged object was negatively charged, electrons move away from the charged object toward the neutral object.

Grounding Step 1 Hand is negatively charged. Faucet is neutral. 11. 2

Grounding Step 2 When the hand is close to the faucet, some electrons from the hand move toward the faucet and create an electric discharge. 11. 2

Grounding Step 3 After grounding, the hand loses its negative charge. The extra electrons go into Earth. 11. 2

Symbol for Grounding 11. 2

Electrostatic Dusters

Electrostatic Precipitators

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