Fundamentals of Electricity and Electronics

7/31/2019 Fundamentals of Electricity and Electronics

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Ohms Law

It is an electrical law that is usedto determine the electrical powerof the electric circuit.

It states that the current througha conductor between two pointsis directly proportional to thepotential difference across thetwo points.


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Ohms Law

Defines the relationship between voltage, current and

resistance.

These basic electrical units apply to direct current, oralternating current.

Ohms Law is the foundation of electronics and electricity.

This formula is used extensively by electricians.Without a thorough understanding of Ohms Law an

electrician can not design or troubleshoot even the

simplest of electronic or electrical circuits.

Ohm established in the late 1820s that if a voltage wasapplied to a resistance then current would flow and thenpower would be consumed.


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George Simon Ohm

Bavarian (German) physicist andmathematician. As a high schoolteacher, Ohm began his researchwith the new electrochemical cell,

invented by Italian scientistAlessandro Volta. Using equipment ofhis own creation, Ohm found thatthere is a direct proportionalitybetween the potential difference(voltage) applied across a conductorand the resultant electric current. Thisrelationship is known as Ohm's law.
http://en.wikipedia.org/wiki/Alessandro_Voltahttp://en.wikipedia.org/wiki/Ohm's_lawhttp://en.wikipedia.org/wiki/Ohm's_lawhttp://en.wikipedia.org/wiki/Ohm's_lawhttp://en.wikipedia.org/wiki/Ohm's_lawhttp://en.wikipedia.org/wiki/Alessandro_Voltahttp://en.wikipedia.org/wiki/Alessandro_Voltahttp://en.wikipedia.org/wiki/Alessandro_Volta


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Symbols being Use in Ohms Law


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Formulas for Ohms Law

V = I x R (Voltage = Current multiplied by Resistance)

R = V / I (Resistance = Voltage divided by Current)

I = V / R (Current = Voltage Divided by Resistance)


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Things to remember:

First, current is inversely proportional toresistance. (What does this mean?)

It means the amount of current will decrease ifwe increase the amount of resistance andmaintain the amount of voltage at its fixed orpermanent value.

Vice versa, if we reduce the amount of loadresistance, current will increase, if the appliedvoltage is maintained at its constant or fixedvalue.


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Second Principle : Current is directlyproportional to voltage.

It simply means that current in the circuitwill increase if we raise or increase theapplied voltage and hold the resistance atits constant or permanent value.


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If you know E and I, and wish to determineR, just eliminate R from the picture and

see what's left:


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If you know E and R, and wish todetermine I, eliminate I and see what's left:


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Lastly, if you know I and R, and wish todetermine E, eliminate E and see what's

left:


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Let's see how these equations might work to help usanalyze simple circuits:

If we know the values of any two of the three

quantities (voltage, current, and resistance) in

this circuit, we can use Ohm's Law to determine

the third.


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calculate the amount of current (I) in a circuit, given values ofvoltage (E) and resistance (R):


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calculate the amount of resistance (R) in a circuit, givenvalues of voltage (E) and current (I):


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calculate the amount of voltage supplied by a battery, givenvalues of current (I) and resistance (R):


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The force

orpressurebehindelectricity


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Fundamentals of Electricity and Electronics