Ohm’s law - Electric Circuits

Ohm’s law



In this lesson, we will learn:

  • A review on the electric circuit and the main components: battery (voltage), closed wire path (current), and devices/resistors that use up electricity (resistance).
  • Also, a review on the main rules/methods we used to solve for each concept individually (voltage and Kirchhoff’s Loop Rule; current and Kirchhoff’s Junction Rule; resistance summation formulas)
  • What is the relationship between voltage, current, and resistance?
  • How to solve circuit problems for voltage, current, and resistance using Ohm’s Law which states that:
    • V=IR V=IR
    • And also, how to rearrange Ohm’s Law: V=IR V=IR ; I=VR I= \frac{V} {R} ; R=VI R= \frac{V} {I}


  • Recall that: a circuit is a closed loop that charge flows within; the three main components of a circuit are voltage (provided by a battery source), current (the rate of flow of charge within the circuit wires), and resistance (a property of the electronic devices using up energy).
    • Voltage is measured in the unit volts (V) which is equal to Joules/Coulomb
    • Current is measured in the unit ampere (A) which is equal to Coulombs/Second
    • Resistance is measured in the unit ohm (Ω \Omega ) which is equal to Volts/Ampere

  • Ohm’s Law states that the voltage is equal to the current multiplied by resistance:
    • V=IR V=IR
    • For metals, resistance is constant and independent of voltage
    • Voltage is directly proportional to current (VI V \propto I)

  • The Ohm’s Law equation can be rearranged to solve for any of the tree main concepts (voltage, current, resistance).
    • V=IR V=IR ; I=VR I= \frac{V} {R} ; R=VI R= \frac{V} {I}
    • The current coming out of a battery is dependent on the resistance of the circuit its connected to

  • Solving questions using Ohm’s Law requires a strong understanding of solving for the three main concepts individually
    • Voltage: Kirchhoff’s 2nd Rule: Loop Rule (sum of all voltages around the loop equal zero); all parallel branches are equal to the same voltage drop
    • st Rule: Junction Rule (sum of all currents into a junction equal to sum of all currents out of the junction) >
    • Resistance: total equivalent resistance in series ( Req(series)=k=1nRk R_{eq(series)} = \sum_{k=1}^{n} R_{k} ) and in parallel (Req(parallel)=1k=1n1Rk R_{eq(parallel)} =\frac{1} { \sum_{k=1}^{n} \frac{1}{R_{k}} } )
  • Intro Lesson
    Introduction to Ohm's Law:
  • 1.
    Solving for Current with a Single Resistor in Series

    Ohm's Law
  • 2.
    Solving for Current and Voltage with Multiple Resistors in Series

    Ohm's Law
  • 3.
    Solving for Current, Resistance, and Voltage for Circuits with BOTH Series & Parallel Configurations

    Ohm's Law
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Ohm’s law

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