Static Electricity

Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it is able to move away by means of an electric current or electrical discharge.
Here are some examples of static electricity in our day to day life:

When we walk on a carpeted floor and getting shock when touching a door knob or any other metal object is one of the best examples of static electricity.
Clothes stuck to one another after being in the dryer is another example of static electricity.

1. Duration: 60 min DPT Medical Physics Lecture 02 Static Electricity Instructor: Engr. Taimoor Muzaffar Gondal [email protected] Lecture 02

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

3. Duration: 60 min DPT Medical Physics Lecture 02 Law of Electric Charges The law of electric charges states that L ike charges repel O pposite charges attract. Protons are positively charged E lectrons 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: The amount of charge (the greater the charge, the greater the force) 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 : Friction Conduction 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 t i res 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 L ightening

15. Duration: 60 min DPT Medical Physics Lecture 01

16. 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

17. 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 t [email protected] Or visit my office during consulting hours This lectures can also be downloaded from https://www.slideshare.net/Taimoor_Gondal