1. Charging by Induction

2. Induction: a definition
the movement of electrons within a substance caused by the approach of a charged object (no contact)

3. Charging by Induction
when charging an object by induction, a charged object is used to induce a charge in a neutral object (without any contact between the two)
in order to do this, you must ground the neutral object
the two objects end up with opposite charges.

4. Charging by Induction, con’t
Grounding is the process of connecting an object to Earth’s surface.
when you connect an object to the ground, you provide a path for charges to travel to or from the ground.

5. How Objects are Discharged

6. Electrical Discharge
once an object is charged, the charges are trapped on it until they are given a path to escape.
when electric charges are transferred very quickly, the process is called an electrical discharge.
this can be caused by induction - the discharge happens before contact actually occurs.
example: sparks or lightning

7. Lightning
Lightning is an example of a very large electrical discharge caused by induction.
in a thunderstorm, a charged area, usually negative, builds at the base of the cloud.
the negative charge at the base of the cloud creates a temporary positive area on the ground through the induction process.
What is lightning?

8. Lightning
when enough charge has built up, the cloud then discharges its excess electrons to the ground, creating a huge spark - lightning.
this discharge creates a rapid expansion of the air around it, causing the sound of thunder. (The lightning bolt is super heated which causes the air around the lightning bolt to become super heated and as a result, the air rapidly expands creating the large boom)

9. Lightning Rods
Every year, millions of dollars of damage is done to property from lightning strikes. This damage can be avoided by the use of lightning rods.
A lightning rod is a metal pole with a wire attached to it that runs down to the ground.

10. Lightning Rods
the electrical charges are more likely to move toward the tallest objects, because it shortens the pathway to the ground
if lightning hits the lightning rod, the flow of electrons is directed harmlessly down to the ground so the building is not damaged.

11. Homework:
Handout (“Check and Reflect”)
Answer # 1 -5,