Electricity and Magnetism

Chapter 13

Electricity H.W pg 351 ques. 1-4 In today's day and age almost nothing

would be possible without electricity. Listening to the radio watching TV or

keeping food cold or frozen would be very difficult.

Electricity is the change from potential electric energy to the kinetic energy of an atoms charge in motion.

Charges Everything on Earth has what we call a charge or

an electrical unit. These charges can be positive or negative just

like in protons and electrons. It is important to know that opposite charges

attract each other, like a magnet to metal. In an atom the nucleus is positive and the

negative electrons around it are held there by the attraction between the opposite charges.

The electrons closer to the nucleus are held tighter than the ones further away.

Charges We saw that charges can change when

something looses or gains electrons. The loos of them will make an atom positive.

And a gain of them will cause the atom to be negative.

When atoms buildup or loose electrons what is created is potential electric energy called static electricity.

So if your hand happen to gain a couple of extra electrons from say your cloths and you go to touch a door, the electrons leap from your hand to the door knob and give you a shock.

When the electrons leap from one place to another and cause a spark its called static discharge.

Circuits A circuit is a complete, unbroken pathway

for electrons to follow. They can have many paths for electrons to follow.

Metal wires are used to make circuits because they are good conductors of electricity.

They are covered by rubber to protect from electrocution. So rubber is a bad conductor of electricity.

Circuits Electrons always move from an area of

more to an area of less electrons. And circuits control this flow from one place to another.

Circuits start and stop the flow using a switch, when closed the flow stops.

They have a source, like a battery or generator.

Circuits The source, or the battery actually separates the

positive and negative charges of a chemical. (battery acid made of zinc)

When they are separated they have potential energy and when the switch is flipped they are made into kinetic electricity by moving the electrons to a place with less amounts of electrons.

We measure electricity in volts. A volt is the amount of energy that lies between the charges or ends of a battery.

Circuits Certain machines need more volts than others.

And therefore might need more batteries. Like a walkman and a remote control car. The currents of batteries only run in one direction.

From + to -, and is called a Direct current (DC) Things that don’t use batteries, like TV’s,

refrigerators and computers use what we call alternating currents (AC).

Alternating CurrentsH.W. pg 359 ques 1-4

An alternating current has electricity running through it in one direction for a period of time, then that current turns around and runs in the opposite direction.

This type of electricity comes from an outlet, which is connected to a source like a generator and you plug whatever you want to be powered into it with a plug.

Magnets A magnet is an object that has a magnetic field.

Due to oppositely charged ends. A magnet has a North and South poles or a + or –

end that are attracted to each other. For something to be magnetic all of the atoms of

that material have to point in the same direction. This allows all of the electrons to cause a

magnetic field in one direction and the protons cause the opposite charge in the other direction.

Magnets If all of the atoms pointed in different directions

the protons and electrons would cancel each other out and the item would not be magnetized.

An electromagnet is a magnet that is made from an iron rod that is wrapped in metal wire and is hooked up to a battery.

These work just like regular magnets, but they have the ability to be turned on and off. Ex: doorbell.

Sources of electricity Power plants use generators to change

different types of energy into electrical energy with turbines.

Water energy is made into hydroelectric energy with damns and turbines.

Solar energy with solar cells & wind energy with windmills.

H.W. pg. 370 ques. 1-10