Transcript Electricity - Cloudfront.net

Electricity
Electrical Charge and Forces

Electrical charge is the property that causes
protons and electrons to attract or repel one
another.
 There are electric charges in clothes that stick
together from the dryer.
 The attraction or repulsion between electrical
charges is called electric force.
 Like charges repel each other and opposite
charges attract each other.
 An
electric field is the effect an electric
charge has on other charges in the
space around it.
 The strength of an electric field is
dependant on 2 things.
 1.
amount of charge producing the field.
 2. distance from the charge.
The further the 2 charges are away from each
other, the less force they feel.
 The closer the 2 charges are, the more force
they feel.

Electric Field Lines
 Lines
pointing in the direction of the
electric field.
 Represent the strength and direction of
the field.
 Electric field is stronger where lines are
closer together.
 Lines point away from a positive charge
and towards a negative charge.
Electric Materials
 There
are 2 ways to describe whether a
substance is able to conduct electricity.
Conductors – materials in which electric
charges move easily.
 1.

Copper, iron, and most other metals.
Insulators – materials in which
electricity does not move easily.
 2.

Glass, rubber, plastic.
Charge Transfer
 Static
electricity is the study of the
behavior of electric charges, including
how it is transferred between objects.
 Charge can be transferred by:
 1.
friction.
 2. contact.
 3. induction.
Friction
 Rubbing
a balloon on your head is an
example of charging by friction.
 Electrons move from your hair to the
balloon because the atoms in the
balloon attract electrons much more
strongly than the atoms in your hair.
 The balloon gets a negative charge and
your hair gets a positive charge.
Contact
 A Van
de Graaf generator charges a
metal sphere and when you touch it you
acquire a charge large enough to make
your hair stand on end.
 The sphere is still charged, but its net
charge is reduced.
Induction
 Induction
is a transfer of charge without
contact between materials.
 Ex: When you walk across the carpet
your hand picks up a net negative
charge.
 When
you reach for a door knob, the
negative charge of your hand causes the
electrons in the doorknob to all move to the
base of the doorknob.
 The doorknob still has a net charge of zero,
but the charges have moved.
Homework Questions

1. What determines whether charges attract
or repel?
 2. Name 2 factors that affect the strength of
an electric field.
 3. List the 3 methods of charge transfer.
 4. Explain and give an example of charging
by friction.
 5. When a glass rod is rubbed with silk, the
glass becomes positively charged. What is
the charge on the silk? Explain your answer.