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Electrical Resistance and Ohm’s Law

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

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Electrical Resistance and Ohm’s Law

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  1. Electrical Resistance and Ohm’s Law

  2. Electrical resistance and ohm’s law(do not write this) • Georg Simon Ohm • 1789-1854 • German • Physicist • HIGH SCHOOL TEACHER!!!!

  3. OHM’s LAW(DO NOT WRITE THIS) • Using equipment he built himself • Determined there was a direct proportionality between voltage applied across a conductor and the resultant current (OHM’s LAW)

  4. Electrical resistance and ohm’s law(take notes) • 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

  5. Electrical resistance and ohm’s law(take notes) • 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)

  6. TAKE NOTES • 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)

  7. Take notes • e.g. After electrons flow through a light bulb, they have less energy than before they went through it (some is used)

  8. TAKE NOTES • 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)

  9. TAKE NOTES V = Voltage (Potential Difference) I = electric current (measured in Amps) R = electrical resistance (measured in Ω)

  10. Take notes • 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

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