Ohm’s Law

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Ohm’s Law

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  1. Ohm’s Law

    Slide 1 - Ohm’s Law

    • Voltage, Current & Resistance
  2. Current

    Slide 2 - Current

    • An electrical current is the flow of electrons through a complete circuit.
    • The brightness of a light bulb is an indicator of the amount of current (or flow) through the bulb.
    • The unit of current is the Ampere (A) or “amp” for short.
  3. The amount of current that flows in a circuit depends on the resistance of the circuit and the voltage of the source.

    Slide 3 - The amount of current that flows in a circuit depends on the resistance of the circuit and the voltage of the source.

    • * In other words, a battery does not supply a constant amount of current.
    • Current is Variable
  4. Voltage

    Slide 4 - Voltage

    • Voltage is the push that drives flow of electrons.
    • Voltage in a circuit is determines by the source
    • * Batteries will also supply a set amount of voltage (ex. 1.5V, 9V, 12V)
    • The unit of voltage is the Volt (V).
  5. Electrical Potential Energy

    Slide 5 - Electrical Potential Energy

    • Voltage is the result of a difference in electrical potential energy.
    • This is similar to gravitational potential energy, which makes balls roll down hills.
    • In this case charges flow from areas of high potential to low potential.
  6. Resistance

    Slide 7 - Resistance

    • Resistance is an obstacle to the flow of electrons.
    • The total resistance of the circuit impacts the amount of current in the circuit.
    • The unit of resistance is the Ohm (Ω).
  7. Insulators & Conductors

    Slide 8 - Insulators & Conductors

    • Different materials and objects have different resistances
    • Some objects have a set resistance – like nichrome wire
    • Some objects have a variable resistance – like a lightbulb, which has a different resistance when cold v. hot.
    • The resistance of an object depends on how tightly the atoms hang on to their electrons.
  8. Ohm’s Law

    Slide 10 - Ohm’s Law

    • “The current flow through a conductor is directly proportional to the potential difference and inversely proportional to the resistance.”
    • In other words: V = IR  any of these three values can be found as long as the other two are known.
  9. Resistance in a Circuit

    Slide 11 - Resistance in a Circuit

    • When elements are added in series, their total resistance is equal to the sum of their individual resistances:
    • Each bulb has a resistance of 0.2 Ω.
    • The wire and switch have insignificant resistance.
    • What is the total resistance of the circuit?
  10. 0.5 Ω

    Slide 12 - 0.5 Ω

    • 0.3 Ω