Lesson 7 Electricity is a kind of energy

Lesson 7

� Electricity is a kind of energy. Have you ever rubbed a balloon on your head and then stuck it to a wall? If so, you charged the balloon with electricity. � The electrical force that holds a balloon to the wall is called static electricity. Static electricity is electricity held in one place on the surface of an object.

The nucleus contains protons which contain a positive charge. Neutrons do not have any charge and are neutral. The electrons contain a negative charge. In an object that conducts electricity the electrons can move freely from atom to atom as long as they are replaced by another one in their spot. In Non-conductors the electrons cannot pass from atom to atom. This means that if an atom gains or losses electrons it will contain a negative or positive charge.

� Think back to what an atom looks like with its protons, neutrons and electrons.

� When you touch a metal doorknob, for example, electrons can jump and give you a shock. Static charges build up on clouds until they can hold no more. At that point, lightning can occur. � The study of electricity where the charges are not moving is called electrostatics

Law of electric charges: Like Charges repel one another, and unlike charges attract one another. � Think of magnets. The opposites attract each other and the like charges repel each other.

�A static shock can be very powerful, but it is not very useful. In order to run electrical devices, we need a steady flow of electricity. The steady flow of electricity is called an electric current.

� Electric current is very similar to a flowing river. The river flows from one spot to another and the speed it moves is the speed of the current. The size of the current flow is related more to the size of the river than it is to the speed of the river. � A river carries more water each second than a stream, even if both flow at the same speed. With electricity, current is a measure of the amount of charge transferred over a period of time.

�A material that is a good conductor gives very little resistance to the flow of charge. This flow of charge is called an electric current. A good conductor has high conductivity.

� Metals are traditional conducting materials. You see them around the house all of the time. It's a metal wire or one of the metal prongs in an electric plug. There a lot of free electrons in metallic conductors. � Free electrons are electrons that are not being held in atoms, and so, can move easily. � Some of the best metallic conductors are copper (Cu), silver (Ag), and gold (Au).

� In order for electricity to be useful it must be converted into different forms of energy. � Electrical energy is converted into the following: �Heat �Light �Motion �Sound (really a component of motion)

� By wrapping the wire around a metal object the magnetic field can be magnified. This will also give the object a distinct North and South end.

An electric motor is all about magnets and magnetism: A motor uses magnets to create motion. So if you have two bar magnets with their ends marked "north" and "south, " then the north end of one magnet will attract the south end of the other. On the other hand, the north end of one magnet will repel the north end of the other (and similarly, south will repel south). Inside an electric motor, these attracting and repelling forces create rotational motion.

� In the above diagram, you can see two magnets in the motor: The armature (or rotor) is an electromagnet, while the field magnet is a permanent magnet (the field magnet could be an electromagnet as well, but in most small motors it isn't in order to save power).

FOSSIL FUEL GENERATING STATIONS � Fossil fuel generating stations can use three main types of fuel; Oil, coal and natural gas. The gas is burned, and the chemical energy released is used to heat water and produce steam (1). � The high pressure steam is then used to turn a set of fanlike wheels called turbines (2).

1. 2. 3. 4. the fuel is burned to boil water to make steam the steam makes a turbine spin the spinning turbine turns a generator which produces electricity the electricity goes to the transformers to produce the correct voltage

� Coal and oil-fired facilities account for the majority of air emissions from the electric power sector. Emissions -Carbon dioxide -Sulphur dioxide -Particulate matter Environmental issues due to pollutants -Toxic metals - Acid Rain -mercury - Smog - Nitrous oxides - toxic substances -Climate change

� Wind power is created by using windmills. The wind turns giant rotors that turn electromagnetic generators. These generators then send the power to transformers which then convert the voltage to a useable amount before it is sent into distribution. These can now be seen popping up all over Canada.

� The sun is used to knock elections off atoms. The electrons flow then creates a current which must be converted into AC by an inverter.

� Methane produced from rotting garbage and waste is burned. This is then used to heat water and use the steam to turn a turbine to create electricity.

1. MECHANICAL ENERGY � Mechanical energy can be directly converted into electrical energy. � Piezoelectric crystals can produce small amounts of energy when they are squeezed or stretched.

2. THERMAL ENERGY � Thermal energy can be converted into electrical energy using a device called a thermocouple.

3. SOUND ENERGY � Every time you use the telephone you are producing electrical energy as you speak into the mouthpiece. � Sound can be converted into electrical energy by using piezoelectric crystals or by moving magnets and electromagnets.

4. RADIANT ENERGY � Solar cells convert light energy directly into electricity when light strikes the surface of silicon, electrons are released and produce an electric current.

5. CHEMICAL ENERGY �A very common source of electrical energy from a chemical reaction is the voltaic cell.

PARTS OF AN ELECTRIC CIRCUIT Every circuit essentially has 4 parts to it. 1. The source of electrical energy ◦ This can range from a battery, to a generation station. Electrical Load 2. ◦ Anything that converts electrical energy into whatever form of energy needed. The load is the reason that the electrical load exists

PARTS OF AN ELECTRIC CIRCUIT 3. Connectors ◦ Anything that conducts electricity, this can include wires to anything that is metal. 4. Electric circuit control device A simple knife switch, thermostat or any other device that can control the flow of electricity. ◦ When electricity can make a complete circuit it is referred to as Closed Circuit ◦ When electricity cannot make a complete circuit it is referred to as a Open Circuit ◦

ELECTRIC CIRCUIT DIAGRAMS AND SYMBOLS � Conductor �To or wire pass current very easily from one part of a circuit to another.

ELECTRIC CIRCUIT DIAGRAMS AND SYMBOLS � Cell-Supplies �The electrical energy positive end is bigger than the negative end.

ELECTRIC CIRCUIT DIAGRAMS AND SYMBOLS � 2 Cells

ELECTRIC CIRCUIT DIAGRAMS AND SYMBOLS � DC Source- Electrical energy source �DC = Direct current, always flows one way

ELECTRIC CIRCUIT DIAGRAMS AND SYMBOLS � AC Source - Electrical energy source � AC = Alternating current, continually changing direction

ELECTRIC CIRCUIT DIAGRAMS AND SYMBOLS � Ground �A – connection to earth

ELECTRIC CIRCUIT DIAGRAMS AND SYMBOLS � Switch - An on-off switch allows current to flow only when it is in the closed (on) position

ELECTRIC CIRCUIT DIAGRAMS AND SYMBOLS � Lamp �A transducer which converts electrical energy to light

ELECTRIC CIRCUIT DIAGRAMS AND SYMBOLS � Resistor �A resistor restricts the flow of current,

ELECTRIC CIRCUIT DIAGRAMS AND SYMBOLS � Ammeter �-Device that measures current A

ELECTRIC CIRCUIT DIAGRAMS AND SYMBOLS � Voltmeter � -Device that measures voltage V

ELECTRIC CIRCUIT DIAGRAMS AND SYMBOLS Motor -electrical load that converts electrical energy into movement M

� Voltage is the electrical force, or "pressure", that causes current to flow in a circuit. Take a look at the diagram. Voltage would be the force that is pushing the water (electrons) forward. If the water pressure is increased, more water will flow through the pipe with more energy.