Charging by Contact 11.2 1.You can charge a neutral object by rubbing it with a different material (friction). 2.Sometimes, you can charge an object just

Charging by Contact 11.21. 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: Friction11.2

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


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


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

furebonite stronger

ebonite

negatively

furpositively


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.

11.2

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

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.

negativeneutral

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

has shared its electrons with the pith

ball and they are now both

________________ charged.

negativeneutral

electrons

rod

pith ball

negatively

negative

e-

*** The neutral object gets the ___________ charge as the charged object since the charged object shares its charge with the neutral object.


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.


Before After

Neutral Positive

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.


Before After

Neutral Positive

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 __________________.


electrons

electroscope rod

positively

lost

repel / separate

Handout: Charging by CONDUCTION

NeutralElectroscope

____ ChargedElectroscope

+++

+ ++ +

+++

+ ++ +

+++

+ ++ +

+++

+ ++ +

Figure 1

e-e-

Neg

NeutralElectroscope


+++

+ ++ +

+++

+ ++ +

+++

+ ++ +

+++

+ ++ +

+++++ +++++


Figure 2

e-

e-

NeutralElectroscope


+++

+ ++ +

+++

+ ++ +

+++

+ ++ +

+++

+ ++ +

+++++ +++++


Figure 2

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 1Hand is negatively

charged.Faucet is neutral.

Grounding 11.2

Step 2When 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 3After grounding, the

hand losesits negative charge.

The extraelectrons go into

Earth.

Symbol for Grounding 11.2

Electrostatic Dusters

Electrostatic Precipitators

Homework

p. 477 # 1-8

Documents

Charging by Contact 11.2 1.You can charge a neutral object by rubbing it with a different material (friction). 2.Sometimes, you can charge an object just