Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Atoms… Have neutrons, protons, and electrons. Have neutrons, protons, and electrons. Protons are positively charged Protons are positively charged Electrons are negatively charged Electrons are negatively charged

Electrons… Are located on the outer edges of atoms…they can be moved. Are located on the outer edges of atoms…they can be moved. A concentration of electrons in an atom creates a net negative charge. A concentration of electrons in an atom creates a net negative charge. If electrons are stripped away, the atom becomes positively charged. If electrons are stripped away, the atom becomes positively charged.

Electrons… Are located on the outer edges of atoms…they can be moved. valence Are located on the outer edges of atoms…they can be moved. valence A concentration of electrons in an atom creates a net negative charge. anion A concentration of electrons in an atom creates a net negative charge. anion If electrons are stripped away, the atom becomes positively charged. cation If electrons are stripped away, the atom becomes positively charged. cation

The world is filled with electrical charges:

What is this electrical potential called?

Static Electricity The build up of an electric charge on the surface of an object. The build up of an electric charge on the surface of an object. The charge builds up but does not flow. The charge builds up but does not flow. Static electricity is potential energy. It does not move. It is stored. Static electricity is potential energy. It does not move. It is stored.

Static Discharge… Occurs when there is a loss of static electricity due to three possible things: Occurs when there is a loss of static electricity due to three possible things: Friction – rubbing (direct contact) Friction – rubbing (direct contact) Conduction – direct contact Conduction – direct contact Induction – through an electrical field (not direct contact) Induction – through an electrical field (not direct contact)

Electricity that moves… Current: The flow of electrons from one place to another. Current: The flow of electrons from one place to another. Measured in amperes (amps) Measured in amperes (amps) Kinetic energy Kinetic energy

How can we control currents? With circuits. With circuits. Circuit: is a path for the flow of electrons. We use wires. Circuit: is a path for the flow of electrons. We use wires.

There are 2 types of currents: Direct Current (DC) – Where electrons flow in the same direction in a wire. Direct Current (DC) – Where electrons flow in the same direction in a wire. The devices you plug in to a wall The devices you plug in to a wall

2nd type of current: Alternating Current (AC) – electrons flow in different directions in a wire Alternating Current (AC) – electrons flow in different directions in a wire The current in buildings and houses The current in buildings and houses

There are 2 types of circuits: Series Circuit: the components are lined up along one path. If the circuit is broken, all components turn off. Series Circuit: the components are lined up along one path. If the circuit is broken, all components turn off.

Series Circuit

2 nd type of circuit: Parallel Circuit – there are several branching paths to the components. If the circuit is broken at any one branch, only the components on that branch will turn off. Parallel Circuit – there are several branching paths to the components. If the circuit is broken at any one branch, only the components on that branch will turn off. Most houses and buildings are wired this way Most houses and buildings are wired this way

Parallel Circuit

Conductors vs. Insulators Conductors – material through which electric current flows easily. Conductors – material through which electric current flows easily. Insulators – materials through which electric current cannot move. Insulators – materials through which electric current cannot move.

Conductors vs. Insulators Conductors – material through which electric current flows easily. Conductors – material through which electric current flows easily. Conductor – makes music “flow” from the orchestra Conductor – makes music “flow” from the orchestra Conductor – makes train “flow” smoothly down tracks Conductor – makes train “flow” smoothly down tracks Insulators – materials through which electric current cannot move. Insulators – materials through which electric current cannot move.

Examples Conductors: Conductors: Metal Metal Water Water Insulators: Insulators: Styrofoam Rubber Plastic Paper

SEMICONDUCTORS Semiconductors are materials that essentially can be conditioned to act as good conductors, or good insulators, or anything in between. Common elements such as carbon, silicon, and germanium are semiconductors. Can you find them on the Periodic Table? What do they have in common? Silicon is the best and most widely used semiconductor.

Diodes Diode device is a one way valve that controls the flow of electricity – LED lights are the best example LED = Light Emitting Diode Transistors are used to amplify electrical signals (like in a radio)

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

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

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

Difference b/t Volts, Amps, Ohms Difference b/t Volts, Amps, & Ohms Example – you could say that… Example – you could say that… Current (amps) measure how much water comes out of a water pipe. (amount) Current (amps) measure how much water comes out of a water pipe. (amount) Voltage (volts) measure how much pressure is behind the water. (force) Voltage (volts) measure how much pressure is behind the water. (force) Resistance (ohms) measures the friction against the inside of the water pipe Resistance (ohms) measures the friction against the inside of the water pipe

Ohm’s Law Resistance = Voltage / Current Resistance = Voltage / Current Ohms = Volts / Amps Ohms = Volts / Amps

Practice with Ohm’s Law OhmsVoltsAmps

Difference b/t volts & watts If volts x amps = watts Then force of electricity x amount of electricity how powerful it is Remember,how much water? P = w / t how much time?

Properties of Magnets All magnets have two areas of strongest force, called poles. All magnets have two areas of strongest force, called poles. Each magnet has one north pole and one south pole. Each magnet has one north pole and one south pole. Like poles repel, and opposite poles attract. Like poles repel, and opposite poles attract. The magnetic region where you can “feel the force” is called a magnetic field. The magnetic region where you can “feel the force” is called a magnetic field.

Magnetic Materials What makes some things magnetic, while other things can’t be magnetized? What makes some things magnetic, while other things can’t be magnetized? Spinning electrons cause small magnetic fields around each atom. Spinning electrons cause small magnetic fields around each atom. Magnetic materials have atoms whose magnetic fields can be lined up in the same direction. Magnetic materials have atoms whose magnetic fields can be lined up in the same direction. Areas where atoms’ magnetic fields line up are called magnetic domains. Areas where atoms’ magnetic fields line up are called magnetic domains. magnetic domain Randomly arranged domains = No magnet! Randomly arranged domains = No magnet! Magnetic domains lined up = Magnet! Magnetic domains lined up = Magnet!

The Earth is a magnet! magnetic north pole geographic north pole magnetic south pole magnetic south pole geographic south pole Magnetic lines of force around the earth are like the field lines around a giant bar magnet. Magnetic lines of force around the earth are like the field lines around a giant bar magnet. The magnetic north pole and the geographic north pole are not located in the same place! The magnetic north pole and the geographic north pole are not located in the same place! The north pole of a compass points to the earth’s magnetic north pole. The north pole of a compass points to the earth’s magnetic north pole.

Electricity to Magnetism In 1820, H.C. Oersted discovered that an electric current flowing through a wire had a magnetic field around it. In 1820, H.C. Oersted discovered that an electric current flowing through a wire had a magnetic field around it. Electricity can cause magnetism! Electricity can cause magnetism! Electromagnets are powerful magnets that can be turned on and off. Electromagnets are powerful magnets that can be turned on and off. You can make an electromagnet stronger by You can make an electromagnet stronger by 1. putting more turns of wire in the coil 2. making a larger iron core, 3. increasing the current through the wire.

What is an electromagnet? Electromagnet – a magnet made from a current bearing coil of wire wrapped around an iron or steel core. (ferromagnetic core) Electromagnet – a magnet made from a current bearing coil of wire wrapped around an iron or steel core. (ferromagnetic core) Solenoid – the coiled wire that gets wrapped around the core. Solenoid – the coiled wire that gets wrapped around the core.

Uses for electromagnets A simple DC electric motor contains a permanent magnet, an electromagnet, and a commutator. When current flows through the electromagnet, it turns within the magnetic field of the permanent magnet, changing electricity to mechanical energy. A simple DC electric motor contains a permanent magnet, an electromagnet, and a commutator. When current flows through the electromagnet, it turns within the magnetic field of the permanent magnet, changing electricity to mechanical energy. Current meters also use permanent magnets and electromagnets. When current flows through a wire, it makes an electromagnet. The force between the electromagnet and the permanent magnet makes a needle move on the meter. Current meters also use permanent magnets and electromagnets. When current flows through a wire, it makes an electromagnet. The force between the electromagnet and the permanent magnet makes a needle move on the meter.

Magnetism to Electricity Joseph Henry and Michael Faraday discovered that magnetism could also produce electric current. Basis of alternating current. Joseph Henry and Michael Faraday discovered that magnetism could also produce electric current. Basis of alternating current. If a magnet is moved back and forth through a coil of wire, current can be made to flow through the wire. This is the idea behind electric generators and transformers. If a magnet is moved back and forth through a coil of wire, current can be made to flow through the wire. This is the idea behind electric generators and transformers. Current moves left in wire. Current moves right in wire.

Uses for Electromagnetic Induction Generators produce AC current for home and industrial use. Water, wind, or steam are used to move large electromagnets through the coils of wire to produce current. Generators produce AC current for home and industrial use. Water, wind, or steam are used to move large electromagnets through the coils of wire to produce current. Transformers are used to step up voltage of electricity that must travel long distances through wires. Other transformers then step down the voltage before it enters our homes. Transformers are used to step up voltage of electricity that must travel long distances through wires. Other transformers then step down the voltage before it enters our homes.

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

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

That’s It !!!! That’s It !!!!