Notes 6 - Electricity

What is electricity? Electricity - the movement of electrons in a material toward an area of positive (+) charges. Since electrons are negative, they are attracted to positive charge and repelled by negative charge

Potential Difference (voltage) Why aren’t birds on power lines electrocuted? Because there is no potential difference between its feet.

What is voltage? Voltage – the potential energy difference that makes charged particles move Without voltage, electricity will not flow Just like a falling ball, a charged particle moves from high potential energy to low potential energy The greater the difference between the high and the low, the greater the voltage

Batteries are voltage sources Every electric device needs a voltage source in order to work 9 volt battery has two terminals: a negative (-) and a positive (+) with a 9V potential difference between them The negative terminal is the high The positive terminal is the low

How does a battery work? A common battery is filled with a pasty mixture When in use a chemical reaction within the paste strips electrons from a carbon rod. These electrons collect on the zinc exterior of the battery forming the negative terminal

What is current? Current – the rate at which electric charges move through a conductor Just like a ball rolling down hill, the electric charges will move faster if they move down a bigger hill. The greater the voltage the faster the current will flow current flows from the negative terminal of a battery to the positive terminal

What is resistance? Resistance – The friction that slows down moving charged particles As charged particles move through a material they bump into other particles – this creates friction or resistance The more resistance the less current This friction produces heat The filament of a light bulb gets so hot it glows

Electrical Conductors electrical conductors allow charged particles to flow easily They have low resistance Metals like copper, zinc and gold, make the best electrical conductors

Electrical Insulators electrical insulators do not allow electrons to move they have a high resistance Plastic, wood, rubber and glass are all insulators

Use of Conductors & Insulators Free electrons in the copper allow the electric charge to flow through the wire. Insulators: The structure of the rubber does not allow the flow of electrons. ( electrons remain in place )

Ohm’s Law the amount of resistance must be calculated using Ohm’s Law Ohm’s Law states that: resistance = voltage/current R = V / I Why the I and not C? C was already used for something else

Electricity Term Description Unit of measure Formula Voltage Current Resistance

Electricity Term Description Unit of measure Formula Voltage Pushes current forward Volts (V) V = IR Current Resistance

Electricity Term Description Unit of measure Formula Voltage Pushes current forward Volts (V) V = IR Current The rate at which charged particles move Amps (A) I = V R Resistance

Electricity Term Description Unit of measure Formula Voltage Pushes current forward Volts (V) V = IR Current The rate at which charged particles move Amps (A) I = V R Resistance Holds current back Ohms () R = V I