Electronics Technology The Importance of current, resistance, voltage & ohms law.

Helping Your Raspberry PI Survive You

Glenn Mossy

gmossy@yahoo.com

~

June 2013

Some Kind of User Group (SKUG)

Points I’m going to cover

Ohms Law

• Fundamental Units

• Ohm’s Law

• LED Resistor Example

Ohm’s Law Practical Use Example• Going Further with Ohms Law

Current shown Graphically!!

6.24 x 1018 electrons

ConductorGiven Point

1 Coulomb

Rate of Electron flow(CURRENT) is

1 Coulomb per second(1 AMPERE)

1 C = 1 A x 1 second

1 Coulomb moved . .

Ohm’s Law States that

• The current is directly proportional to the voltage and indirectlyproportional to the resistance.

Hydraulic Analogy

• Electricity might be compared to water:

• A battery could be likened onto a water pump.

• Voltage (V) or water pressure (pounds per square inch).

• Current could be likened onto the flow rate of water.

• Coulombs per second = Amperes (A) or gallons per minute.

• A wire is analogous to a water hose.

• Squeezing the hose is Resistance (R) on the water hose.

• An open switch is like a closed valve . .

• Ohm’s original Law was determined when capacitance and inductance was still not studied in detail.

• So that Ohm’s Law can be used in any circuit including Alternating current circuits:

• Modification:

• The current is directly proportional to the voltage and indirectlyproportional to the impedance.”

Ohm’s Law then & now!

Questions

References

• Wikipedia: http://en.wikipedia.org/wiki/Ohm's_law

• Circuitlab Website: https://www.circuitlab.com

• Care and Feeding of LED’s: http://www.thebox.myzen.co.uk/Tutorial/LEDs.html

• Spice Info: http://bwrcs.eecs.berkeley.edu/Classes/IcBook/SPICE/

• Physics Classroom: http://www.physicsclassroom.com/Class/circuits/u9l3c.cfm

• Experiments: http://www.juliantrubin.com/bigten/ohmlawexperiments.html

• Ohm Unit: http://en.wikipedia.org/wiki/Ohm_(unit)

Georg Simon Ohm

“Die galvanische Kette”

Faraday

1836

Maxwell 2nd Great Unification in Physics

1879

Kirchoff

1845

Henry

1831

Helmholtz

1842

Ohm’s Law’s Importance

Kleist & Muschenbrook

1746

Galvani

1780

Volta

1800

Fourier

1822

1827

Getting starting with your experiments