A battery or power outlet creates the electromotive force that makes a current of electrons flow.
Compare to horse power? Moving a big create of electrons?
Wiring Part 1: basic electricity
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The entire study of electricity is based on the Electron Theory - This assumes that all electrical and electronic effects are due to the movements of electrons from one place to another- = ?Before we work with electricity we must know what an electron is and what causes it to move -Lets look first at where we find electrons…in atoms
The atom is the building block of all stuff, or what scientists call "matter". Electrons have a negative charge.- + Protons have a positive charge. Neutrons are neutral and therefore have no charge. What things are made of atoms?0
- In an Electrically Neutral Atom: The number of protons=the number of electrons + + So how many - + electrons will there be?- + It is the movement of - these electrons between different atoms that creates electricity
The flow of electrons is called the current Lots of - Attracted toelectrons - +ve –ve - The units of current is amps
Historic physicists did not know about atoms and electrons when they created the rules for electricity. They knew it was charge that moved but they didn’t know if it was +ve or –ve. They assumed +ve and that’s what the rest of electrical rules have been based onThe only way it can work is that the real negativesflowing in one direction are replaced with imaginarypositives flowing in the other.This is the waywe will continue - -ve ve -veto think ofcurrent from now = G Conventionone G al Current Electron +v +v +ve Flow e e
For electricity to flow, there has tobe something to push the electrons EMFalong. This is called an electromotive force (EMF) A battery or power outlet creates this Electromotive force which induces current in a circuit. EMF is measured in volts
The difference in EMF across two points is called the potential difference. (change in electrical potential energy) What is the potential difference of this light bulb?3volts 5 volts 5 volts-3 volts =2 volts So where have the 2 volts gone? They have been transferred from - + electrical energy into light energy.
Not all materials give up their electrons easily.Remember that metals give up Non electrons easily whereas non metal- metals do not give away high electrons readily resistanceThis reluctance to give awayelectrons is called resistance. Metal-low resistance - - -- - - - - - - -- -- - - - Low Resistance High Resistance
Do these materials high have high or low resistance? high high low low
A BPower=work done -Work done= moving an electron from one place to another Power is measured in Watts Power =EMF x Current Watts= Volts x Amps Current - - - EMF - - - Power =
Power =EMF x Current Watts= Volts x Amps What is the power of CFL bulb ? (CFL stands for compact filament lamp) EMF=2 volts Current=11 amps What is the power of filament bulb? EMF=8 volts Current=11 ampsWhich is better to use and why?
Work done in a period of time Units=Kilowatt Hours (kwh) Kilowatt Hours (kwh)= power x time = EMF x current x time - - - EMF - - -Power =
A hand grinder in the Vigyan Ashram workshop has apower rating of 800 watts. It runs for 20 minutes asession and is used 2 times a day. Calculate the dailyelectrical energy that is needed in kwh.Length of time on a day Convert to hours=2 times x 20 minutes =40 mins=40 minutes /day 60 mins/hour =0.66 hourElectrical Energy = 800 watts x 0.66 hour =52.80 watt hours =0.0528 kilowatt hours
The water pump at Vigyan Ashram uses 4.4kwh a day. Itis on for two hours a day. If the EMF of the pump is 230volts what is the current used?Electrical energy used Electrical Energy= EMF x current x timein one hour=4.4kwh a day Current= Electrical Energy 2 hours a day EMF= 2.2 kw = 2200=2200 watts 230 =9.56 amps
1. What direction does conventional current go? +ve -ve2. What is resistance? Name a material that has high resistance and low resistance.3. What is EMF and what is its units.4. How can you find the power of an appliance if you know the EMF and current? X5. How is electrical energy different from power?