Current Electricity

Current Electricity is due to a charged electrical particle called an Electron.

Two or more charges that are alike repel each other. Two or more charges that are opposite attract each other. Properties of Charged Particles

Current The charge pump creates the FLOW of charged particles. This is called a CURRENT.

Current is symbolized by the letter I. It is measured in amperes, A.

LIKE HEAT…. When the ends of an electric conductor are at different electric potentials, charge flows from one end to the other. This means there is a potential difference, or voltage.

The amount of work needed to move charges a certain distance is known as Voltage or Potential Difference.

Voltage A measure of the energy available to move electrons The electrical potential difference between two points Voltage is measured like potential energy Voltage drops as it gets used

Voltage Sources Dry Cells-Batteries Wet Cells Generators

Electric Current Direct Current Flows in 1 Direction Only DC is produced when stored electrical energy is tapped Batteries and Solar Cells have this electrical potential Alternating Current changes direction periodically AC is produced by a generator

Power A charge moving in a circuit expends energy. This might result in heating the circuit, or turning a motor. The rate at which electrical energy is converted to another form, such as mechanical, heat or light, is called Electric Power.

Electric Power=Current x Voltage =ampere x volt watt = watt P= I x V

Example 2-A 6 volt battery delivers 0.5 A of current to an electric motor connected across its terminals. What is the power of the motor? What energy does the motor use in 5 minutes?

Resistance Resistance: Measure of how easily current flows through a circuit -- higher resistance: harder for charge to go through -- Low Resistance: easier for charge to go through

Resistance increases current goes down Resistance decreases current goes up Resistance is measure in Ohm’s Two types of resistors --Fixed: always has the same value --Variable: value changes

Ohm’s Law OHM’S LAW Discovered in the 18 th century Ratio between potential difference and the current flowing through the wire Law states: “the current that flows through a given wire varies directly with the applied voltage” Formula: I=V/R or V=IR

Ohm’s Law-Current Flow Symbol for ohm is (see board); 1 ohm is the resistance which permits a current of 1 A to flow between a voltage of 1 To obtain a higher voltage, higher charge is needed; higher voltage=electric field to be more intense=more electrons to move

Effects of Various Electric Current on the Body Current in AmpsEffect 0.001Can be felt 0.005Painful 0.010Muscle Spasms 0.015Loss of Muscle Control 0.070Fatal if longer than1 sec

Series Circuit Current can ONLY travel in 1 path

Series Circuit-math Formula to find “total resistance” R T = R 1 + R 2 + etc To find the current flow: use Ohm’s Law The sum of the voltage is equal to the voltage of the entire circuit put together

Series Circuit Series Circuit- break in the circuit, stops the current Resistors connected in “series”, the current travels through EACH resistor exactly the same way Current encounters resistance by each resistor; opposed by the sum of the resistors; total resistance is the sum

Parallel Circuit Current can follow many paths

Parallel Circuit Placing resistors in parallel always decreases the total resistance of the circuit! Total resistance decreases because each new resistor has a “different” path for the electrons to flow

Parallel Circuit-Math Formula to find total resistance for a parallel circuit: 1/R T = 1/R 1 + 1/R 2 + 1/R 3 + etc Total current is the “sum” of the currents in the separate branches Voltage is equal to the voltage of the generator