Ohms law

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Intros
Lessons
  1. Introduction to Ohm's Law:
  2. What have we learned about voltage, current and resistance?
  3. What does Ohm's Law tell us about circuits?
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Examples
Lessons
  1. Solving for Current with a Single Resistor in Series


    Ohm's Law
    1. Find the current flowing in the circuit.
    2. If the battery is connected to the circuit for 30 seconds, how much charge passes through the resistor?
      1. 4.0 C
      2. 120 C
      3. 500 C
      4. 3000 C
  2. Solving for Current and Voltage with Multiple Resistors in Series

    Ohm's Law
    1. Find the current coming out of the battery.
    2. Find the voltage used up by each resistor.
  3. Solving for Current, Resistance, and Voltage for Circuits with BOTH Series & Parallel Configurations

    Ohm's Law
    1. Find the current across each resistor.
    2. Find the value of resistor RE.
    3. Find the voltage of the battery.
Topic Notes
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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 Kirchhoffs Loop Rule; current and Kirchhoffs 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 Ohms Law which states that:
    • V=IR V=IR
    • And also, how to rearrange Ohms Law: V=IR V=IR ; I=VR I= \frac{V} {R} ; R=VI R= \frac{V} {I}

Notes:

  • 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

  • Ohms 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 (V∝I V \propto I)

  • The Ohms Law equation can be rearranged to solve for any of the three 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 Ohms Law requires a strong understanding of solving for the three main concepts individually
    • Voltage: Kirchhoffs 2nd Rule: Loop Rule (sum of all voltages around the loop equal zero); all parallel branches are equal to the same voltage drop
    • Current: Kirchhoffs 1st 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)=1∑k=1n1Rk R_{eq(parallel)} =\frac{1} { \sum_{k=1}^{n} \frac{1}{R_{k}} } )