Introduction to static electricity

1. Introduction to Electricity
• In this unit we will be studying:
• Static electricity
• Current electricity
• Power generation.

2. • Did you ever walk across a carpet,
touch something and get a shock?
That shock was caused by static
electricity. The science of static
electricity is called electrostatics.
Static ElectricityStatic Electricity

3. • The word ‘static’ means not moving
• Static electricity means electrons are
not moving along a path or not flowing
(current electricity).
• Rather electrons are supplied from one
atom and moved onto another atom
resulting in a build-up of charge.
Static ElectricityStatic Electricity

4. Subatomic
Particles
Charge
Location in
atom
proton
positive (+) nucleus
neutron
no charge (0) nucleus
electron
negative (-)
orbiting the
nucleus

5. If an object has more
electrons than protons,
it is negatively charged.
Electric ChargeElectric Charge
# protons: 8
# electrons: 12
# protons < # electrons
therefore, overall charge = negative

6. if an object has more
protons than electrons,
it is positively charged
Electric ChargeElectric Charge
# protons: 8
# electrons: 5
# protons > # electrons
therefore, overall charge = positive

7. If an object has an equal
number of protons and
electrons, the object is neutral
Electric ChargeElectric Charge
# protons: 8
# electrons: 8
# protons = # electrons
therefore, overall charge = neutral

8. Electric ChargeElectric Charge
+ —
Law of attraction: opposite charges attract

9. Electric ChargeElectric Charge
+
—
Law of repulsion: like charges repel
+
—

10. Electric ChargeElectric Charge
+
—
A charged object and a neutral object
will attract each other
0
0

11. • Electrons can be transferred from one
object to another.
• For example, a neutral or positively
charged object will become negatively
charged if it gains electrons.
Electric ChargeElectric Charge

12. • Similarly, a neutral or negatively
charged object will become
positively charged if it loses
electrons.
Electric ChargeElectric Charge

13. Only electrons (negative
charges) are capable of
moving from one object to
another!
Protons (positive charges)
stay in place.
Electric ChargeElectric Charge

14. • Conductivity is the ability of materials to
allow electrons to move freely
• Materials that hold on to their electrons
and do not allow them to move easily
are called electrical insulators
• Materials that allow electrons to change
positions are called conductors
Conductors & InsulatorsConductors & Insulators

15. InsulatorsInsulators
+—
+
—
+
—
+—
+—
+
—
+—
In an insulator, the electrons (-) are bound tightly
to the nuclei (+) so they resist movement

16. Common InsulatorsCommon Insulators

17. ConductorsConductors
+
—
+
—
+
—
+
—
+
—
+—
+
—
In a conductor, the electrons are not as tightly bound to
the nuclei and can therefore move away from the nuclei

18. Common ConductorsCommon Conductors

19. Detecting ChargesDetecting Charges
• There are different instruments used to
detect charged objects:
– Pith Ball Electroscope
– Metal Leaf Electroscope
• In both instruments neutral position of
leaves/ball changes when charged
object is place closeby

20. Pith Ball ElectroscopePith Ball Electroscope
• A pith ball electroscope
consists of a neutrally
charged ball of pith (plant
material) and non-
conductive string and
stand
• When charged object
brought close to ball, the
ball will be attracted to it

21. Metal Leaf ElectroscopeMetal Leaf Electroscope
• A metal leaf electroscope is more sensitive to electric charge
than a pith ball electroscope
• When charged object brought close to metal ball or cap, the
leaves will repel each other and spread apart

22. Videos and Practice Questions
• https://www.youtube.com/watch?v=yc2-363MIQs
• https://www.youtube.com/watch?v=QxZ6AWLpnUw
• https://www.youtube.com/watch?v=oU8Fe6846d4