The document is a lecture on static electricity and electric charge, explaining the properties of protons, electrons, and neutrons, and how electric charges interact according to the law of electric charges. It details the methods of charging objects (friction, conduction, induction) and introduces the concept of static electricity and electric discharge. Additionally, the document discusses lightning, grounding, and the safety measures associated with it, including the use of lightning rods.

1. Duration: 60 min DPT Medical Physics Lecture 02
Static Electricity
Instructor:
Engr. Taimoor Muzaffar Gondal
taimoor.muzaffar@superior.edu.pk
Lecture 02

2. Duration: 60 min DPT Medical Physics Lecture 02
Electric Charge
All matter is made up of atoms and atoms contain
1. Protons (+)
2. Neutrons (0)
3. Electrons (-)

3. Duration: 60 min DPT Medical Physics Lecture 02
Law of Electric Charges
The law of electric charges states that
 Like charges repel
 Opposite charges attract.
 Protons are positively charged
 Electrons are negatively charged, so they are attracted to each other.
 Without this attraction, electrons would not be held in atoms.

4. Duration: 60 min DPT Medical Physics Lecture 02
Law of Electric Charges

5. Duration: 60 min DPT Medical Physics Lecture 02
Electric Force
The force between the charged objects is an electric force.
The size of the electric force depends on 2 things:
1. The amount of charge (the greater the charge, the greater
the force)
2. The distance between charges (the further the distance, the
less the force)

6. Duration: 60 min DPT Medical Physics Lecture 02
 An electric field is the region around a charged object
where electric forces can be exerted on another charged
object. (Repelled or attracted)
Electric Field

7. Duration: 60 min DPT Medical Physics Lecture 02
How Objects get Charged
There are 3 ways objects can be charged:
1. Friction
2. Conduction
3. Induction
**In each of these, only the electrons move. The protons stay in the nucleus**

8. Duration: 60 min DPT Medical Physics Lecture 02
Friction
Charging by friction occurs when electrons are “wiped” from one object
onto another.
Ex.
If you use a cloth to rub a plastic ruler, electrons move from the
cloth to the ruler.
The ruler gains electrons and the cloth loses electrons.

9. Duration: 60 min DPT Medical Physics Lecture 02
Induction
Charging by induction happens when charges in an uncharged object are
rearranged without direct contact with a charged object.
Ex.
If you charge up a balloon through friction and place the balloon
near pieces of paper, the charges of the paper will be rearranged
and the paper will be attracted to the balloon.

10. Duration: 60 min DPT Medical Physics Lecture 02
Conduction
Charging by conduction happens when electrons move from one object
to another through direct contact (touching).
Ex.
Suppose you touch an uncharged piece of metal with a positively
charged glass rod. Electrons from the metal will move to the glass rod.
The metal loses electrons and becomes positively charged.

11. Duration: 60 min DPT Medical Physics Lecture 02
Static Electricity
Static electricity is the electric charge at rest on an object.
When something is static, it is not moving.
The charges of static electricity do not move away from the object
that they are in. So, the object keeps its charge.
Ex. Clothes taken out of a dryer

12. Duration: 60 min DPT Medical Physics Lecture 02
• The loss of static electricity as charges move off an object is called
electric discharge.
• Sometimes, electric discharge happens slowly.
• Ex: Clothes
• Sometimes, electric discharge happens quickly.
• Ex. wearing rubber-soled shoes on carpet, lightning

13. Duration: 60 min DPT Medical Physics Lecture 02
Why do gasoline tankers usually have
metal chains at the back?
When cars run, their tires and bodies are usually charged by _______. For
gasoline tankers, if the accumulated charge is large enough, _______can be
produced and _________ will occur if gasoline vapor is ignited. Those metal
chains conduct the charge on the bodies of tankers to the _______ and avoid the
danger.
friction
sparks
explosion
ground

14. Duration: 60 min DPT Medical Physics Lecture 02
Lightening

15. Duration: 60 min DPT Medical Physics Lecture 01

18. Duration: 60 min DPT Medical Physics Lecture 02
Lightning usually strikes the highest point in a charged area because that point
provides the shortest path for the charges to reach the ground.
Anything that sticks up or out in an area can provide a path for lightning.
A lightning rod is a pointed rod connected to the ground by a wire.
Objects, such as a lightning rod, that are joined to Earth by a conductor, such as a
wire, are “grounded.” Any object that is grounded provides a path for electric
charges to move to Earth.
Because Earth is so large, it can give up or absorb charges without being damaged.
When lightning strikes a lightning rod, the electric charges are carried safely to
Earth through the rod’s wire. By directing the charge to Earth, the rods prevent
lightning from damaging buildings.
Lightening

19. Duration: 60 min DPT Medical Physics Lecture 02
End of Lecture 02
For any kind of queries and questions you are advised to
write at
taimoor.muzaffar@superior.edu.pk
Or visit my office during consulting hours
This lectures can also be downloaded from
https://www.slideshare.net/Taimoor_Gondal