Unit 9 - Electricity

Unit 9 - Electricity

By S Harris

I know...

• the 3 ways to charge an object

​​Learning Target

I can...

• explain the transfer of electrons between 2 objects

​​Success Criteria

REVIEW...

Atoms are composed of 3 main parts:

• In the nucleus

  • protons (p⁺; positive)

  • neutrons (n⁰; neutral)

• In the cloud

  • electrons (e^-; negative)​

And EVERYTHING is made of atoms.

Electric Charge

Protons and Electrons have a property called ELECTRIC CHARGE.

• recall that an atom has an equal number of protons and electrons (so these positive and negative charges will cancel each other out)​

• Recall also that electrons can be transferred/moved from one atom to another (this is called ELECTRIC CURRENT)

Protons do NOT move, but Electrons do!

The total number of electrons and protons between the two objects will remain the same because the LAW OF CONSERVATION OF CHARGE says that charges cannot be created or destroyed, only transferred.​

Items such as:

• fur/hair

• wool

• silk​

​will easily lose (give up) their negative charges (e^-) to other items so that they can become positively charged.

There are several ways to charge an object:

1. friction

2. induction

3. conduction (direct contact)​

static electricity

​

tranferring charges due to rubbing objects together

• example: walking across a carpet with sock on​

Friction

Involves the charging of one object by another object without direct contact.

• examples:

  • balloon and rice cereal

  • electroscope ​

Induction

Involves the direct contact of a charged object

to a neutral object.

• example:

  • Van de Graaf generator

Conduction

​

Objects can't hold a static charge forever. This is because they prefer equilibrium (which means that they want to be neutral).

• static discharge occurs when electrons move towards equilibrium.

Static Discharge

How do we know which objects allow electricity to flow?

These items allow the easy flow of electricity.

• Loosely bound electrons that are free to move from atom to atom

​​Conductors

Insulators

​

These items resists the flow of electrons

• hold more tightly to their valence electrons (on the outermost shell)