Electricity & Magnetism https://www.youtube.com/watch?v=XSukRnxGy5c

Recall: Electrons are located in the electron cloud outside the nucleus. Electrons have a negative charge. If electrons are removed from the atom, the atom becomes positively charged. *If you lose something negative, you become more positive!

What is static electricity? The build up of an electric charge on the surface of an object. The charge builds up, but DOES NOT flow. Static electricity is potential energy. It does not move. It is stored.

What is static discharge? Occurs when there is a loss of static electricity due to three possible things: Friction - rubbing Conduction – direct contact Induction – through an electrical field (not direct contact) COMPLETE: *Fur and Rod activity*

What is electricity that moves? Electric Current: The flow of electrons from one place to another. Measured in amperes (amps) Kinetic energy Controlled with circuits. Circuit: is a path for electrons to flow. We use wires.

There are 2 types of currents: Direct Current (DC) – Alternating Current (AC) Electrons flow in different directions in a wire. Electrons flow in the same direction in a wire.

There are 2 types of circuits: Series Circuit: Parallel Circuit Only one path for electrons to take. If the circuit is broken, all light bulbs turn off. Several pathways for electrons to travel. If the circuit is broken at one branch, only the light bulbs on that branch turn off.

What is Voltage? The measure of energy given to the charge flowing in a circuit. The greater the voltage, the greater the force or “pressure” that drives the charge through the circuit.

What is the difference between Volts and Amps? For example, you could say that… Amps measure how much water comes out of a hose. Volts measure how hard the water comes out of a hose.

Ohm’s Law The voltage across an ideal conductor is proportional to the current through it. Formula: Ohms = Volts Amps

What is an electromagnet? Electromagnet – A magnet made from a current bearing coil of wire wrapped around an iron or steel core. When a switch turns on electricity, it moves through the wire. The magnetic field is formed in the same direction as the electric current.

What is magnetism? A force of attraction or repulsion due to electron arrangement. Magnetic forces are the strongest at the poles Magnets have two poles: North and South

Magnetic Poles and Fields Magnets always have two poles If a magnet is cut, it will still have two poles! Like magnetic poles repel. Unlike magnetic poles attract. A magnetic field is the area in which magnetic forces act.

Earth’s Magnetic Properties Earth’s magnetic field is called the magnetosphere. Earth’s magnetic field is strongest at the poles. Magnetic fields of the Earth and other planets are related to their cores. Earth’s magnetic field is generate from its iron core. Compass needles are magnetized and respond to the magnetic field of the Earth. Compasses point towards Earth’s North Pole.

What affects magnetic properties? Dropping, hammering, or heating a magnet will cause a magnet to lose magnetic properties.

Additional SLides

What is a generator? Generator – A machine that changes mechanical energy to electrical energy Usually use moving magnets to create currents in coils of wire.

What is Resistance? The opposition to the flow of an electric current, producing heat. The greater the resistance, the less current gets through. Good conductors have low resistance. Measured in ohms.

What Influences Resistance? Material of wire – aluminum and copper have low resistance Thickness – the thicker the wire the lower the resistance Length – shorter wire has lower resistance Temperature – lower temperature has lower resistance

Practice with Ohm’s Law

What is a motor? Motor – a device that changes electrical energy to mechanical energy that can do work.

Questions What two forces are involved in magnetism? Which subatomic particle accounts for magnetism? Explain the interaction between magnetic poles when they are close together.

Questions Which scientist described the Earth’s magnetic properties? Name the devices used to indicate geographic direction based on the Earth’s magnetic field. What is the name of the Earth’s magnetic field? Where is the Earth’s magnetic field the strongest?