Electric Charge and Electric Force

Electric Charge and Static Electricity

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Electric Fields

• An electric field is a region around a charged object where the object's electric force is exerted on other charged objects.

• Because positive charges are repelled by positive charges.. and attracted to negative charges..field lines point away from positive charges and towards negative charges

How Does Charge Build Up?

• Most atoms are uncharged, or neutral because the protons equal the electrons.

• Uncharged objects become charged by gaining or losing electrons

• Static electricity is the buildup of charges on an object

• In static electricity, charges build up on an object, but they do not flow in a current

Charging Objects

• Charges are neither created nor destroyed. This is known as the law of conservation of charge.

• If one object loses electrons, another object must pick them up

• There are four methods by which charges can redistribute themselves: Friction, conduction, induction, polarization

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Charging by Friction

• Charging by friction is the transfer of electrons from one uncharged object to another by rubbing objects together

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Charging by Conduction

• When a charged object touches another object, electrons can be transferred

• This is the process of transferring electrons by direct contact

Charging by Induction and by Polarization

• Electrons can react to the electric field of a charged object without touching the object itself. This is induction

• Polarization occurs when electrons move only within their own atoms. In this case, the electrons create charged ends of the atoms

Multiple Choice

True or False:
In static electricity, charges build up on an object, but they do not flow continuously.

• True
• False
• 11
• Tuesday

Multiple Choice

Rubbing a balloon on hair is an example of static charge build up created by....

• conduction
• friction
• induction
• hairduction

Multiple Choice

The girl's hair and the comb are attracting  one another.  The hair and the comb have

• opposite charges
• like charges

Multiple Choice

If an object has the same number of positive and negative charges, its electrical charge is...

• positive
• negative
• neutral or no charge
• opposite

Multiple Choice

An object becomes postiively charged when which of the following occurs?

• loses electrons
• gains electrons
• loses protons
• gains neutrons

Multiple Choice

What is static electricity caused by?

• A balance of power

• A balance of positive and negative charges

• An imbalance of positive and negative charges

• An imbalance of protons and neutrons

Multiple Choice

Which of the following is caused by static electricity?

• a stove getting hot when it is turned on
• a magnet being attracted to a refrigerator
• a lightning strike during a storm
• a light bulb coming on when a switch is turned on

Multiple Choice

What happens when you touch a metal doorknob after rubbing your shoes on the carpet?

• The doorknob sends a burst of electric current into your body
• Millions of electrons go from your finger into the doorknob
• The doorknob sends millions of electrons into your finger
• our finger becomes negatively charged

Multiple Choice

If a substance has a higher number of electrons than protons on its surface, what type of charge does it have?

• A positive charge.
• A negative charge.
• A neutral charge
• No charge at all

Multiple Choice

Mrs. Davis rubbed two balloons with a piece of wool. What will happen when the balloons are brought near each other?

• The balloons will repel each other.

• The balloons will attract each other.

• The balloons will become positively (+) charged.

• The balloons will pop.

Multiple Choice

A student is investigating how a negatively charged rubber rod affects how charges are distributed on two stainless steel spheres that are touching each other. A diagram that shows two steps of the investigation is shown.

Which diagram for step 2 correctly predicts the distribution of charges on the stainless steel spheres?