- Slides: 32
ENERGY SOURCE: ELECTRICITY Recall where charge comes from in the atom Protons: positive charge Neutrons: no charge, neutral Electrons: negative charge Only electrons are free to move! Law of electric charges: unlike charges attract like charges repel Neutral objects are attracted to charged objects
ACTIVITY: LIKE AND UNLIKE CHARGES Examine the labeling on a dry cell A. which end produces electrons? Which end has a deficit? Explain. B. Predict what will happen if you connected the ends (terminals) with a wire. Use the law of charges to support your answer. C. Test your prediction, but for no longer than 5 seconds! *this creates a short circuit that rapidly drains the cell of energy. What did you observe?
What is the difference between Static electricity and Current Electricity?
TYPES OF ELECTRIC CHARGE : STATIC Static charge is charge at rest; NOT moving Objects rub against one another (friction) and transfer charge (creates static electricity) Van de Graff generator - As belt moves rapidly over rollers, the contact results in transfer of charge onto the metal dome, which can be transferred to objects - Sparks when the build up is “discharged”
TYPES OF ELECTRIC CHARGE : CURRENT Current electricity refers to electric charges flowing in a circuit through a conductor. What moves? Electrons!
CURRENT ELECTRICITY This is electricity that flows from one place to another Many examples of current electricity are easy to spot because they use cords/wires plugged into an outlet in the wall; other devices use batteries
CHALLENGE MIT - Lighting a lightbulb Can you light a light bulb with one wire, one light bulb and 1 battery?
ELECTRIC CIRCUITS A complete pathway that allows electrons to flow is called an electric circuit. Electrons flow through devices (loads) in the circuit that convert electricity to other forms of energy.
ACTIVITY: CIRCUIT PUZZLES
ACTIVITY: CONDUCTOR OR INSULATOR?
WHAT TYPES OF MATERIALS ALLOW ELECTRONS TO FLOW? These are called conductors Metals are the best conductors of electricity (electrons allowed to travel freely) Materials that prevent electricity (electrons) flowing freely are called insulators
PARTS OF AN ELECTRIC CIRCUIT There are four important components to a circuit: 1. Energy Source a. Chemicals – ionic compounds in solution – ions float freely and the electrons are allowed to move through the solution to complete a circuit b. Electric cell - (we mistakenly call it a battery, a battery is actually 2 or more cells combined). c. In houses - power comes from an outside source. (In BC = Hydro power)
ELECTRIC CELL Diagram: A battery is 2 or more electric cells 2 Types of Batteries: Primary – not rechargeable – can’t reverse the reactions Secondary - rechargeable
PARTS OF AN ELECTRIC CIRCUIT 2. Load - converts electrical energy into another form of energy (light, heat, sound etc. ) Without a load, connected batteries would burn out quickly! Examples of a load: Dishwasher, stove, microwave, stereo, tv, light-bulb Motor Resistor Light bulb
PARTS OF AN ELECTRIC CIRCUIT 3. Conductor – wire where the electrons (current) flows, Used to connect and complete the circuit 4. Switches – to open (on) or close (off) your circuit Other components in a circuit: Meters – to measure amount of � Voltage � Current
ELECTRICAL CIRCUIT explanation
Draw a picture of a circuit with a cell, a bulb and connecting wires
CIRCUIT DIAGRAM A schematic that simplifies the information
CIRCUIT DIAGRAM - SYMBOLS motor fuse resistor ammeter
CIRCUIT DIAGRAMS 1 cell, 1 switch, 1 light bulb You try: 2 cells, 1 motor, 1 light bulb controlled by one switch. How would you have to arrange them if you want to control them by separate switches?
If we wanted to connect two batteries, how would we do it?
SERIES VS. PARALLEL Arrangement of Cells
CIRCUITS IN SERIES
SERIES VS. PARALLEL Arrangement of loads (ex. Light bulbs) Series – There is only a single pathway for current to flow Parallel – Current splits up between the different pathways
SERIES VS. PARALLEL CIRCUITS Types of Circuits
PRACTICE Drawing Electric Circuits Sheet Ammeters are drawn directly on the wire, on the same path as a light bulb Voltmeters are drawn across a load (device), if there is one in the circuit
PERMIT #2 Circuits in Series and Parallel