Charging by Contact 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.

Charging by Contact: Friction 11.2 What is the charge on the hair? What is the charge on the comb? neutral neutral

11.2 What is the charge on the hair? What is the charge on the comb? positive negative After combing 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. Charging by Contact: Friction 11.2 electrostatic series

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

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. When the fur and ebonite are rubbed together, some electrons from the __________ move to the ______________ because ebonite has the ______________ attraction for electrons. Since the _____________ gains electrons, it becomes ________________ charged. Since the _____________ loses electrons, it becomes ________________ charged. stronger fur ebonitestronger ebonite negatively fur positively

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

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.

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. Handout: Charging Objects by CONDUCTION The _____________ on the negatively charged rod repel each other and jump from the _________ to the ________________. The negative rod has shared its electrons with the pith ball and they are now both ________________ charged. negative neutral

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. Handout: Charging Objects by CONDUCTION The _____________ on the negatively charged rod repel each other and jump from the _________ to the ________________. The negative rod has shared its electrons with the pith ball and they are now both ________________ charged. negative neutral electrons rod pith ball negatively negative e-e-

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

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. Handout: Charging Objects by CONDUCTION BeforeAfter NeutralPositive

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. Handout: Charging Objects by CONDUCTION BeforeAfter NeutralPositive

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

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

Handout: Charging by CONDUCTION Figure 2 e-e- e-e-

Handout: Charging by CONDUCTION Figure 2 e-e- e-e- 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 11.2 Step 1 Hand is negatively charged. Faucet is neutral.

Grounding 11.2 Step 2 When the hand is close to the faucet, some electrons from the hand move toward the faucet and create an electric discharge.

Grounding 11.2 Step 3 After grounding, the hand loses its negative charge. The extra electrons go into Earth.

Symbol for Grounding 11.2

Electrostatic Dusters

Electrostatic Precipitators

Homework p. 477 # 1-8