electrical resistance and ohm’s law
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Electrical Resistance and Ohm’s Law. Electrical resistance and ohm’s law(do not write this). Georg Simon Ohm 1789-1854 German Physicist HIGH SCHOOL TEACHER!!!!. OHM’s LAW(DO NOT WRITE THIS). Using equipment he built himself - PowerPoint PPT PresentationTRANSCRIPT
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Georg Simon Ohm 1789-1854 German Physicist
HIGH SCHOOL TEACHER!!!!
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Using equipment he built himself Determined there was a direct
proportionality between voltage applied across a conductor and the resultant current (OHM’s LAW)
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Good conductors easily allow electrons to move through their atoms
In a good conductor little energy is lost as the electrons pass along the conductor’s atoms
In other materials such as a light bulb the electrons do not move as easily.
This ability of a substance to impede the flow of electrons is called electrical resistance
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In other materials such as a light bulb the electrons do not move as easily.
This ability of a substance to impede the flow of electrons is called electrical resistance
Different loads have different resistances to achieve the desired conversion of energy
e.g. : light bulb filament = high resistance (produces light)
toaster = lower resistance (produces heat) The symbol for electrical resistance is R The standard unit is (SI) is the Ohm (Ω)
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The symbol for electrical resistance is R The standard unit (SI) is the Ohm (Ω) When electrons flow through different
materials, the electrical resistance causes a loss of voltage
There is a difference in the amount of voltage (electric potential) that an electron has after it has flowed through the material
This is known as potential difference or voltage drop
e.g. After electrons flow through a light bulb, they have less energy than before they went through it (some is used)
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e.g. After electrons flow through a light bulb, they have less energy than before they went through it (some is used)
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Ohm’s Law Ohm’s Law describes the relationship
between potential difference and current in a conductor
Potential difference = electric current x Electrical Resistance
(voltage drop)
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V = Voltage (Potential Difference)I = electric current (measured in Amps)R = electrical resistance (measured in Ω)
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V = IxR (units for V are Volts) V/I = R or R = V/I (Units for R are Ω) V/R = I or I = V/R (Units for I are Amps) Sample problem: What is the voltage drop across the
tungsten filament in a 100W light bulb? The resistance of the filament is 144 Ω and the current is 0.833A.
V = ? I = 0.833A R = 144 Ω V = I x R V = 0.833A x 144 Ω = 120V Therefore the voltage drop at the light
bulb is 120V