Electricity and Magnetism Key PointsStandard: SPS10

April 15, 2014

How Can You Charge Objects?

There are 3 ways objects can be charged:1. Friction2. Conduction3. Induction

**In each of these, only the electrons move. The protons stay in the nucleus**

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.

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. 

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.

Series Circuits

I. Series Circuit: the current has only one loop to flow through

things are wired one right after the other If one thing (bulb) goes out every thing goes

out If the circuit is broken the entire flow of current

stops

Series Circuit

Current is the same at each point in the circuit

When another resistor (light bulb) is added in series, the total resistance increases.

When resistance increases, current will decrease.

Decreased current means dimmer light.

II. Parallel Circuit: contains two or more branches for current to move through

current splits up to flow through the different branches

because all branches connect the same two points of the circuit – the voltage difference is the same in each branch

more current flows through the branches that have the lower resistance

Alternating and direct current

The current from a battery is always in the same direction.

One end of the battery is positive and the other end is negative.

The direction of current flows from positive to negative.

This is called direct current, or DC.

Alternating and direct current

If voltage alternates, so does current.

When the voltage is positive, the current in the circuit is clockwise.

When the voltage is negative the current is the opposite direction.

This type of current is called alternating current, or AC.

The force or pressure behind electricity

• Permanent magnets are created by placing material, such as iron, into a very strong magnetic field. This will allow the material to maintain the magnetic properties even after being removed from the field.

• An electromagnet is a temporary magnet created by coiling a wire around a metal core, and passing a current through the wire.

• An electric motor is a device which converts electricity to mechanical energy.

• An electromagnet turns inside of a permanent magnet. By changing the direction of the current, the poles will keep switching between N and S, and therefore cause the electromagnet to continually rotate. (pg. 236)

• Electric motors are used in most household appliances which convert electricity into motion.