**The flow of electronsM Tommasi

**Electric current Static electricity is the..The flow of e- in a wire is called an electric currentMore e- implies greater current.It is measured in Amperes (amps)The symbol is the letter I

**ResistanceIt is the opposition to the flow of electrons.It is what makes some wires better conductors.It changes electricity into light or heatIt is measured in ohmsThe symbol is R

**VoltageTo move object we need to push themElectrons can be pushed alsoThat push is called voltageThe bigger the push the higher the voltageIt is measured in voltsThe symbol is V

DonowGive an example of a load.What does a switch do to a circuit?What is the main difference between a series and a parallel circuit?Draw a series circuit containing a power source, a switch and 2 loads?What happens in a series circuit that contains a power source, a switch and 2 light bulbs if one light bulb blows out?**

ReviewingCurrent (I) is the flow of electrons in a circuitVoltage (V) is how hard the electrons are pushedResistance (R) is the friction of electric flow. **

**PossibilitiesCan you have A) high current and high voltage?B) high current and low voltage?C) low current and high voltage?D) low current and low voltage?

**Ohms lawA locomotive can push a train of cars against friction at a velocity.If theres a lot of friction it can push only a few carsTo push a lot of cars it has to push harder The amount of push a locomotive can provide depends on the friction and number of cars.

Ohms law**In electricity voltage is the locomotiveThe voltage equals the current x resistanceV = I x RIf theres more resistance you have to push harder If you want to move more electrons you have to push harder

Problem 1**A voltage has to push electrons through a load or resistorProblem: What voltage is needed to push a current of 5 amps through a light bulb that has a 4 ohms resistance inside it?V = I x R V = 5 x 4 = 20 volts

**Question 2What is the current going through a wire that has a resistance of 30 ohms if the voltage pushing the electrons is 45 volts?V = I x R45 = I x 30I = 45/30I = 1.5 ?

DonowWhat is voltage?What is current?What is resistance?What voltage is necessary to push 3 amps of current through a 4 ohm resistor?What current can go through a 5 ohm resistor if 4 volts are pushing it?**

Electrical powerThe power needed to run an appliance depends on the voltage and the current Every appliance needs a different amount of power to workPower = voltage x currentP = V x IIn the US the voltage in any regular outlet is always 120 volts**

ExampleHow much power is used by a light bulb if the voltage across the light bulb is 120 V and the current going through it is 2 amps?P = V x IP = 120 x 2 = 240 watts.**

exampleWhat power is being used by a hair dryer if the current going through it is 10 amps?Power = voltage x currentPower = 120 x 10Power = 1200 watts **

**Two types of current Electrons can be pushed in 2 different waysThey can be pushed out directly from one point and go into another (DC or Direct Current)The electrons can be made to go back and forth (AC or Alternating Current)

**Creating DC (direct current)DC can be created in several ways1) wet cell-using liquid acid and two different metals to chemically release electronsCar batteries are a kind of wet cells2) dry cell-using an acid paste instead of liquid acid to release electronsThese are the regular batteriesCells always have a voltage of 1.5 V

**Creating a DC current 3) battery- a group of cells working togetherThats a 9-volt battery4) Solar cells- pure silicone sheets that use sun light to push electrons

**Creating (AC) alternating currentA magnet is moved back and forth near a wireAs the magnet moves the electrons are pushed back and forthThe current changes directionIn the US the current changes direction 60 times a second (60 Hz)

Creating alternating currentAC current is made by blocking a river (Dam) and allowing the escaping water to turn a turbine (hydroelectric).Or by boiling water and letting the steam turn the turbineThe heat to boil the water can be made by burning coal, oil or nuclear power.**

Electrical safetyNever handle an appliance with wet hands or while standing in waterNever run wires under a carpetDont connect too many appliances to the same circuitGet rid of extensions if they are damagedNever stick metals inside electrical appliancesNever come too close to fallen power lines.**