1. Electrical Potential When charges are within an electric field an electrical potential difference is created. Volt – unit of measurement for potential difference. (electrical potential, voltage) Voltage is the prime mover in electrical systems (like pressure in fluid system).

2. Electrical Potential Fluid systemElectrical system Flow caused by “potential” difference Current – Flow

3. Sources of Difference A pump is a source of fluid pressure difference A battery is a source of electrical potential difference

4. Components of Electrical Systems Voltage source (battery or generator) Conductors (wires or circuit board) Load (motor, lights, etc.) Control element (switch) Voltage source Control Electrical Load Electrical circuit

5. AC vs. DC Direct Current (DC) – charge flows in one direction. Batteries Solar Panels Alternating Current (AC) – charge flows back and forth. Alternators Generators

6. Batteries Cell – a single unit housing one or more chemical. Battery – consist of several cells How does it work? Chemicals react and electrons are removed creating a potential difference (voltage) Primary Cells – one time use batteries (cannot be recharged) Secondary Cells – Can be recharged

8. Connecting cells Electrodes – the positive and negative terminals on a battery (cell). Positive electrode (red) called anode. Negative electrode (black) called cathode. Voltages add when cells are connected in series. Battery + ++ - -- 1.5 v 3.0 v 1.5 v

9. A Simple DC Circuit

10. AC Circuits An AC voltage source reverses the positive and negative terminals many times per second. The current flows one direction and then the other then the other….. This changing of polarity or cycling is called frequency, measured in cycles per second (hertz).

11. AC vs DC

12. Where does AC come from? The main source of 60hz current comes from electrical power plants, through power lines and into your homes. Generally 110 – 120 volts Some larger electrical devices need 220 – 240 volts.

13. Summary Newton’s law of universal gravitation and Coulomb’s law are both inverse squares laws. The magnitudes of both forces decrease with the square of the distance between the masses and the charges. Atoms are composed of proton, neutrons and electrons. Protons are positively charged, electrons are negatively charged, and neutrons have no charge. The flow of electrons in an electrical system is a current. Unlike charges attract, like charges repel.

14. Summary (cont.) An electric field is a model of the alteration of space around one or more charges. You can use the field to predict the force exerted on a charge placed in a the field. The potential difference, or voltage, between two points in a uniform electric field is the product of the field strength and the distance between the points. Voltage is the prime mover in electrical systems. A battery is a source of DC voltage. It can maintain a current in an electrical circuit. Batteries or cells can be connected in series to increase voltage.