What is Electricity? Electricity is the flow of electrical charge because electrons start to move. All matter is made of atoms that contain electrons The wires in your electronic device contains wires made from conductors. As you know, conductors do not hold onto their electrons very easily and only need a little push to get them to flow through the conductor. Setting up a potential difference is all they need to start flowing. A potential difference is when there is an area of high concentration of electrons that want to flow to an area that has a low concentration of electrons.

Flowing Electricity or Current The electricity we are familiar with is usually flowing through our appliances. There are three main parts to flowing electricity. They are: Voltage (V) Current (I) Resistance (R)

Voltage (V) is what we call the Potential Difference Voltage is the push behind the electrons. Imagine electron flow like is like water. A pump can be hooked up to the water to cause it to flow. The stronger the pump, the more water will flow. The pump for electrons is a battery or a generator.

Another way to calculate voltage or potential difference In order to get the water or current to flow, there needs to be a force acting over a distance. The force is the force of attraction between charges calculated in Coulomb’s law. If you remember, force times distance is work (J). In a circuit, we think of the work happening per charge (c). ΔV = Vhigh-Vlow = work q

Voltage is measured in volts. Adding cells to a battery in a circuit can increase the voltage or potential difference in the circuit. Voltage is additive in a circuit.

Measuring Volts Remember the other name for voltage is potential difference. This means there is a difference between the voltage from one terminal of the cell to the other or in two different places on a circuit. 1.5 V The positive side of the cell should have about 1.5 V of current where as the negative side of the cell should have no current or should be zero. 0 V

Voltage drops Voltage drops from one place to another every time it is used. This explains why a single bulb circuit is brighter than a two bulb circuit.

7.2 Current (I) Current is the actual flowing or moving of [e-]. This is just like the current of a river is the flow of water. Current is measured in units called Amperes or amps. Current flows through wires.

Amperes Measuring Current Amperes or Amps is the flow of one coulomb per second. A coulomb is the unit used for electrical charge or the attractive force between charges. Measuring Current To measure current you have to have it flow through the meter.

There are two kinds of current Direct Current (DC) happens when current flows in one direction. Example is Batteries

Alternating Current (AC) is a current that reverses it’s direction continuously. This happens because the electricity is made from a generator and is the kind of electricity that comes from the wall outlet. Generators work by moving magnets through coiled wires. In a generators, this happens very fast.

7.3 Resistance Resistance always resists or opposes the flow of the electrons. It has a unit of Ohms. Anything the current flows through (including the wire) is a resistor. But mainly it is the appliances or light bulbs in the circuit. This example of water is a good way to think about resistance

How the wire itself effects resisitance The longer the wire the more resistance it has The thinner the wire the more resistance it has The hotter the wire the more resistance in the wire

Some resistors are better than others at resisting the flow of current Resistors that allow current to flow easily are called conductors. These are things like metal.

Insulators do not allow current to flow easily if at all.

Electrical Conductivity The property of matter that describes its ability to allow charge to flow.