Unit E: Electrical Applications
Chapter 12: Static and Current Electricity
12.2: Static Electricity and Discharges
pg. 464
Key Concepts:
1. Static electricity is the result of an imbalance of charges
on the surface of an object.
2. There are many useful applications of static electricity
Static Electricity
Static Electricity: an imbalance of electric charge at rest on
the surface of an object.
The imbalance of electric charge on an object’s surface is
static or not moving.
The charges stay in one place, until they suddenly jump to
another object.
Electric Discharge
Electric Discharge: the rapid transfer of electrons from one
object to another.
The sudden movement of a charge from one object to
another is known as an electric discharge. An example
occurs when you rub the socks on your feet through the
carpet on the floor. Electrons from the carpet move to you,
you become negatively charged. When you reach for the
metal door knob, the negative electrons jump from you to
the door knob, neutralizing your charge, creating a shock
and a small spark.
Lightning
A lightning bolt is an example of a natural electric
discharge. There is a difference between the charge of the
clouds and the ground, between two different clouds, or
parts of clouds.
Water and ice particles swirling around in the clouds can
become charged. Positive charged particles move to the top
of the cloud, while negatively particles move to the bottom.
The ground becomes positively charged. When the charge
difference becomes large enough, there will be an electric
discharge, known as lightning. The air expands very
quickly, causing a loud noise known as thunder.
Figure 2: The imbalance of
charge between a cloud and the
ground results in a brilliant
flash of lightning.
Uses of Static Electricity
There are many uses of static electricity.
Static-cling Film
Static-cling decals are used for signs on windows of
buildings, homes and cars. Some are used on windows to
filter out sunlight rays. The oppositely charged parts are
attracted to each other.
Photocopiers
An image is captured by a scanner is converted by a laser
beam. The laser beam is projected onto a drum creating a
negatively charged pattern. Positively charged ink (toner) is
attracted to the pattern on the drum. The ink toner is then
passed onto the paper, recreating the image.
Figure 5: a) The laser “draws” a negatively charged image on the drum. b) The drum rolls
across the positively charged toner, which sticks to the negatively charged laser
“drawing”. c) The drum rolls across paper with a higher negative charge, and the toner
particles “stick” to the paper.
Check Your Learning:
Questions 1 – 6, pg. 467
Wrap Up:
- Static Electricity is an imbalance of charge at rest on the
surface of an object.
- An electric discharge is a sudden movement of electrons
between two objects with different charges.
- Lightning is a natural discharge of electrical energy.
- Static electricity has many real-world applications.
- Static electric discharges can damage electronic devices.