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Resistance, Current and Voltage

Resistance, Current and Voltage. Making Sense of Circuits. Resistance (R). How much an object resists electricity flowing Increasing resistance, lowers the current Measured in Ohms ( Ω ). Equivalent resistance. The combined effect of all resistors

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Resistance, Current and Voltage

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  1. Resistance, Current and Voltage Making Sense of Circuits

  2. Resistance (R) • How much an object resists electricity flowing • Increasing resistance, lowers the current • Measured in Ohms (Ω)

  3. Equivalent resistance • The combined effect of all resistors • Resistors in series and in parallel act very differently

  4. Resistors in Series • The resistances of each light bulb combine to form larger resistance = 10Ω 100Ω 20Ω 130Ω

  5. Resistors In Parallel • Act all crazy • Follow a weird, hard to spot rule (that kind of makes sense) • When we add a light bulb in parallel, we open up a new route for electrons • So the current out of the battery increases, instead of decreasing like in series

  6. Equivalent Resistance in Parallel • 1/R = 1/R1 + 1/R2 + 1/R3 … + 1/R100000 • So if we have 2 bulbs in parallel, each with 10Ω of resistance • 1/R = 1/10 + 1/10 • 1/R = 2/10 • 1/R = 1/5 • R = 5Ω

  7. Find the Equivalent Resistance 1/R = 1/10 + 1/20 + 1/60 1/R = 6/60 + 3/60 + 1/60 1/R = 10/60 1/R = 1/6 R = 6Ω (notice the resistance is LESS than when you just had 1 bulb) 10Ω 20Ω 60Ω

  8. Current (written as I) • Current is the amount of electrons flowing through a conductor, per second • Measured in amperes or Amps (A) • 1A = 6.241x10^18 electrons / second

  9. Voltage (V) • How much “push” there is on electrons • Determines how much energy each electron carries • Determines the current • Voltage is used up by a resistor

  10. How Do the 3 concepts relate? • A voltage causes a current • The more voltage, the more current • A resistor lessens the current • The more resistance, the less the current I = V/R or V=IR

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