Electrical Potential Energy and Voltage

1. Electrical Potential Energy and Voltage Grade 9 Science

2. Electrochemical Cells convert chemical energy to electrical energy. • A Battery is another name for an electrochemical cell, or sometimes several cells joined together.

3. Energy is the ability to do work. • Any moving object has Potential energy. • Kinetic energy is the energy stored in an object.

4. The energy stored in a battery is called Electric Potential Energy, since the electrons have the ability to do work once they leave the battery. In order for the electrons to release their stored energy, the battery must be hooked up to a device.

5. Electric Potential Difference • Remember that charge is measured in Coulombs. • A Volt (V) is defined as the amount of electric potential energy per one coulomb of charge.

6. Producing Voltage • Batteries can be classified into two groups: Dry cells and Wet cells. Dry cells are found in devices like flashlights. Wet cells are found in cars and motorcycles.

7. A battery has two terminals called Electrodes. The electrodes are usually made of two different metals, but can be made of other substances. • The electrodes are in an electrolyte, which is a substance that is able to conduct electricity. • The amount of voltage that is produced by an electrochemical cell depends on the metals and electrolyte used.

8. Other Sources of Energy • Friction (rubbing 2 objects together to produce a charge) • Piezoelectric crystals (when crystals such as quartz are hit or squeezed, they produce a burst of electricity – BBQ lighter)

9. Other Sources of Energy • Photo-electrochemical cells (solar cells) • Thermocouples (a loop of two wires made of different metals that produces electricity when heated or cooled)

10. Other Sources of Energy • Generators (consist of a magnet that is able to generate electricity when it is moving next to a wire. The magnet may be moved using water (hydroelectric) or steam from a nuclear plant.)

11. Electrical Current Grade 9 Science

12. A complete pathway that allows Electrons to flow is called an electriccircuit

13. Any device that transforms electrical energy into another form of energy is called an electric load (ex. heat energy, light energy, sound energy) For example: • A toaster is an electric load that transforms electrical energy into heat energy. • A radio is an electric load that transforms electrical energy into sound energy.

14. Circuit Components and Diagrams • All circuits are made up of four basic types of parts: • Source - The source of electrical energy (ex: a battery). • Conductor - The wire through which electricity flows. • Load - A device that transforms electrical energy into another type of energy (ex: a light bulb) • Switch - For turning the circuit on and off by making or closing a break in the circuit.

15. Circuit diagrams use symbols to show different components in the circuit. • These are the symbols most commonly used in circuit diagrams:

16. A circuit diagram (right) representing an actual circuit (left).

17. When an electrical current travels through a circuit, electrons are pushed from the negative terminal of the battery, through the circuit, and back to the positive terminal of the battery. • The conducting wire (or metal wire), already contains electrons throughout its length, so as soon as the electrons start pushing from the negative terminal of the battery, the current flow starts. • The continuous flow of electrons in a complete circuit is called current electricity.

18. Conventional Current • In 1747, Benjamin Franklin introduced the idea that positively charged objects were bigger than negatively charged particles • He suggested that electricity flows positive to negative • The concept of electron flow to describe current was not accepted until 1800 after electrons were discovered

19. Current: The Measure of Flow • Electric current is defined as the amount of charge passing a point in a conductor every second. Electric current is measured in amperes (A). An ammeter is a device to measure current in units of amperes. Its symbol on a circuit diagram looks like:

20. How do we meet our electrical energy demands?

21. What does this image show?

24. The Flow of Electrons • Unlike static electricity, current electricity involves the FLOW of electrons. • Electrons flow through a conductor in a controlled way. • The steady continuous flow of electrons means that the flow can be used to do work. • Static discharge is unpredictable and random.

25. Electricity Song (to the tune of Frere a Jacque) Electricity Electricity Controlled flow of electrons Controlled flow of electrons Your negative flows towards positive Conductors allow electrons to flow along What’s our source of electrons? What’s our source of electrons? We use hydro Flowing water through a dam Produces electron flow Flow through our town We connect appliances To our walls and that connects Allowing electrons to flow Allowing electrons to flow

26. Conductors and Insulators • Conductors are materials that allow the flow of electrons to move easily through them • Insulators do not allow electrons to flow through them • Semiconductors are materials that allow electrons to flow through them under certain conditions.

28. What do you know about attraction of charged particles?

29. Summary: 1. Current electricity involves the controlled flow of electrons through a conductor. 2. Current electricity moves easily though a conductor and poorly through an insulator. 3. Current electricity requires a source of electrical energy to create a flow of electrons.

30. Assignment • Video of the following: • Different between potential and kinetic energy • Direction of electron flow • Show your definition of current