Physics Unit Chapter 8 – pages 268 – 303

Section 8.1 Electric Potential Energy and Voltage Chapter 8 Section 8.1 Electric Potential Energy and Voltage

Electric Charge How can we separate electric charges? Recall in Chapter 7 We separated charges by rubbing objects together  friction Unlike charges want to come back together  opposite charges attract The further we move unlike charges apart, the more electric potential energy they gain.

Electric Potential Energy What is Electric Potential Energy? Potential Energy – energy stored in an object. Kinetic Energy – energy of motion. Electric Potential Energy – electrons have stored energy and the ability to do work after they leave the battery. Electrons will help convert electrical energy into another type of energy (i.e. heat or light)

Electric Potential Energy and Voltage Electrochemical Cells – converts chemical energy into electrical energy stored in charges. Battery – a combination of one or more electrochemical cells. Brainiac – Electric Fence

Electric Potential Difference The Potential Difference is the change in the amount of electric potential energy per one coulomb of charge  called the voltage Unit of Voltage – Volts (V) Voltmeter – a device that measures the amount of potential difference between two locations of charge separation.

Potential Energy vs. Potential Difference a) climbing stairs b) climbing with a heavy pack on (more work = more potential energy) Potential Energy depends on both height moved and mass moved Potential Difference In a battery, potential difference is like the height of the stairs and the amount of charge separated is like the mass moved up the stairs So in a battery, potential energy is due to both the potential difference (volts) and amount of charge separated (coulombs)

Classifications of Batteries What are two different types of batteries? Dry cells Examples of devices that use dry batteries (flashlights, portable CD players, MP3s, iPods, and watches) Wet cells Examples of devices that use wet batteries (cars, motorcycles, electric motorcycles)

Classifying Batteries Dry Wet

Dry Cell Battery Dry Cell Battery Parts Positive Terminal Carbon Rod Electrolyte Moist electrolytic paste Plastic Insulator Negative Terminal Zinc metal Common disposable battery found in electronic devices

Simple Voltaic Wet Cell Wet Cell Battery Parts Positive Terminal Lead (IV) oxide (PbO2) Electrolyte Sulphuric Acid (H2SO4) Negative Terminal Lead metal (Pb) Common battery found in automobiles, golf carts, etc., can be recharged.

How Batteries Work How do Batteries Work? Batteries have two terminals called electrodes (made of two different types of metals) These electrodes are in an electrolyte (a substance that conducts electricity) The electrolyte will pull electrons off one metal  creating a positive charge on one electrode and a negative charge on the other electrode This produces a potential difference (voltage) between the two electrodes.