Transcript Static Electricity - Madison County Schools

Jag Mark
How do like charges interact? unlike
charges?
Electric Charge
and Static
Electricity
Notes
Electric Charge
• Electric charge is a property of protons
and electrons.
• Protons have a positive charge.
Electrons have a negative charge.
Proton
Electro
n
Electric
Charge
• Two charges that are the same push away from
each other. Two charges that are different pull
toward each other.
• If a proton and an electron come close together,
they attract each other.
• Attraction (pull) and repulsion (push) between
electric charges is known as interaction between
charges. The interaction between charges is
called electricity.
Repulsion
Attraction
Electric Charge
• This is different from the interaction
between magnetic poles, which is
known as magnetism.
• The terms “positive” and “negative”
were given to charges by Benjamin
Franklin in the 1700s.
Electric Charge
• Balloon + Aluminum Can
• Comb + Paper
• Balloon + Water
Electric Force
• Electric force is the attraction or
repulsion between electric charges.
• A magnetic field surrounds a charged
object. An electric field is a region
around a charged object in which
electric force occurs.
Electric Force
• Suppose one charged object is placed
in the electric field of a second charged
object. The first charged object is either
pushed or pulled -- repelled or
attracted.
• The strength of an electric field
depends on how far away the charged
object is. The farther away a charged
object is, the weaker the electric field is.
The strength of an electric field is represented by how
close the electric field lines are to each other.
Static Electricity
• Most objects usually have no charge.
However, objects can become charged.
• If an object loses electrons, it has more
protons than electrons. Therefore, it has
a positive charge.
• If an object gains electrons, it has more
electrons than protons. Therefore is has
a negative charge.
- +
- +
+
+
- - +
- +
+
+
- + - - - -
Before Rubbing
(uncharged)
After Rubbing
(Negatively Charged)
+
Static Electricity
• Static Electricity is the buildup of
charges on an object. Static means “not
moving.” In static electricity, the charges
do not flow or move.
Transferring Charge
• An object becomes charged when
electrons move from one place to
another place.
• Charging by friction is when electrons
move from one uncharged object to
another object by rubbing. For
example, a girl charges by friction when
she runs her socks on the carpet.
Transferring Charge
• Charging by conduction is when
electrons move from a charged object
to another object by direct contact. You
can charge yourself by conduction
when you touch a charged object.
• Think: carpet > socks = friction
• Then: socks > feet = conduction
Transferring Charge
• Charging by induction is when
electrons move to one part of an object
due to the electric field of another
object. There is no touching in charging
by induction.
Transferring Charge
• You can find out if an object is charged
by using an instrument called an
electroscope.
When the object is uncharged, the leaves hang
down, but if a charged object gets close, the leaves
repel each other and spread apart.
Static Discharge
• Charges may build up as static
electricity on an object. But the charges
do not stay on that object forever.
• The loss of static electricity as charges
move from one object to another is
called static discharge.
Static Discharge
• A static discharge often produces a
spark. For example, there may be a tiny
spark when you touch a metal
doorknob. Lightning is another example
of static discharge.