Energy & Voltage

Energy Energy = the ability to do work Electric energy that is moving is kinetic energy Electric energy that is stored is potential energy This is similar to gravitational potential energy Example: If a ball is lifted and held above the ground, the ball has energy because, if released, the ball can do work. But if the ball is not released, then it is said to have potential energy

Energy Electrons separated from the positive nucleus “want” to return to their original location, just like the ball “wants” to return to the ground. If the electrons are held apart, then these e- have electric potential energy. The amount of energy the separated e- possess is dependent upon 2 things: How far they have been separated and How many e- have been separated.

Electrochemical Cells Convert chemical energy into electrical energy. Chemical energy separates the positive from the negative charges (giving them potential energy)

Battery Connecting cells together forms batteries. It is now accepted language to refer to all electrochemical cells as batteries, regardless of the number of cells involved. The ends of batteries are called terminals Terminals are where we make a connection to the battery Extra e- accumulate on one terminal making it negatively charged e- left from the other terminal to accumulate, leaving that terminal positively charged

Batteries change chemical E into electrical E Battery When the battery is connected to an electrical device, e- can flow through the connecting wires The electrical energy is transformed into other forms of energy (eg. Sound, heat, light…) Batteries change chemical E into electrical E

What is Voltage? Voltage is what makes electric charges move; It can be thought of as the force that pushes the charges to move in a wire or other electrical conductor. Since moving charge is a current, voltage can cause a current. Voltage is an electrical potential difference between two places and is always measured between two points. Examples: Between the positive and negative ends of a battery Between a wire and the ground Between a wire or a point of a circuit and a point in another part of the circuit.

Electric Potential Difference Potential difference, or voltage as it is more commonly called, is proportional to the distance that the charges have been separated. The actual potential energy is the product of both the voltage and the amount of charge (Energy = Voltage × Charge) The unit of electric charge is the coulomb (C) One coulomb = 6.25 x 1018 e- gained or lost. That’s 6 250 000 000 000 000 000 electrons!

Electric Potential Difference Potential difference or voltage: the amount of electric potential energy per coulomb of charge The unit of voltage = volt (V) One volt equals one joule per coulomb. The symbol for the unit volt is written with an uppercase V as in (9V). Voltmeter measures the amount of potential difference between two locations

Producing Voltage Batteries come in 2 basic types: Dry Cells: batteries in flashlights, watches, etc. Wet Cells: car batteries Two terminals on a battery are called electrodes Usually made of 2 different metals or a metal + some other material Electrodes are in an electrolyte  substance that conducts e- Amount of voltage produced depends on the types of electrodes used, and the electrolyte

Electrolytes Substance that conduct electrons

Electric Circuits An electric circuit consists of three things: A source of energy (the battery) A load that consumes this energy (perhaps a light bulb) A closed path to carry energy from the source to the load (the wires) The concepts of voltage, charge, current, and resistance can be explained with a bucket of water and a hose attached to the bottom.

Electric Circuits The tank will act as our source (of water). The amount of pressure created at the end of the pipe by the water represents voltage. The water represents charge (and the movement of electrons). The bucket will act as our load (receptacle). The flow of water through the pipe represents current. The width of the pipe represents resistance; a skinny pipe would have less flow than a wider pipe. The pipe is our connecting path between the source and the load and acts as the wire.

Electric Circuits If you were to pour one gallon of water into the bucket while covering the end of the pipe with your thumb, the pressure you feel against the thumb is similar to how voltage works. The potential energy difference between the two points – the top of the water line and the end of the pipe – is just that one gallon of water. Now let's say that you found a bucket large enough to be filled with 450 gallons of water (roughly enough to fill a 6-person hot tub). Imagine the kind of pressure your thumb might feel while attempting to hold that quantity of water back. Definitely more of a 'push.' Voltage (the cause) is what makes current (the effect) happen; without any voltage push to force it, there would be no flow of electrons.