8.1 Electric Potential Energy and Voltage

 A battery is a combination of electrochemical cells connected together  Electrochemical cells convert chemical energy into electrical energy stored in charges  In a battery, chemical energy separates the positive and negative charges  The battery terminals are the end points where connections are made  Extra electrons are at one terminal making it negatively charged  The other terminal has lost electrons so is positive

 Energy is the ability to work  Kinetic energy is energy of a moving object  Potential energy is stored energy  Electric potential energy is the electrical energy stored in a battery since electrons have stored energy and the ability to work after leaving the battery

 The amount of electric potential energy per one coulomb of charge is called the potential difference or voltage  The unit is the Volts (V), named in honour of Alessandro Volta, an Italian physicist who invented the battery  The potential energy of a battery is due to both the potential difference (V) and the amount of charge that has been separated (coulombs)  C, D, AA and AAA all have a potential difference of 1.5 V but the battery that can separate the most charge would have the greatest potential energy

 A voltmeter is a device that measures the amount of potential difference between two locations of charge separation  Batteries are classified into two groups:  Dry cells are batteries with a paste in the middle  Wet cells are batteries with a liquid in the middle  A battery has two terminals called electrodes made of two different metals or materials  The electrodes are in an electrolyte which conducts electricity...moist paste in dry cells and liquid in wet cells

1. Friction – rubbing two materials together can separate charge 2. Piezoelectric crystals – when certain types of crystals (like quartz) are squeezed, positive and negative charges are separated 3. Photo electrochemical cells – made of semi- conducting material such as silicon and when light hits the cell, some of the light energy breaks electrons off the surface of the cell 4. Thermocouples – a long loop of two wires of different metals joined at both ends and when one end is heated or cooled, a charge is separated and a voltage is created 5. Generator – when a wire moves close to a magnet or a magnet moves close to a wire, a voltage is created across the wire