Ohms 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 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:
• $V=IR$
• And also, how to rearrange Ohms Law: $V=IR$; $I= \frac{V} {R}$; $R= \frac{V} {I}$

• 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 ($\Omega$) which is equal to Volts/Ampere


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


• The Ohms Law equation can be rearranged to solve for any of the three main concepts (voltage, current, resistance).
• $V=IR$; $I= \frac{V} {R}$; $R= \frac{V} {I}$
• 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 2^nd Rule: Loop Rule (sum of all voltages around the loop equal zero); all parallel branches are equal to the same voltage drop
• Current: Kirchhoffs 1^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 ( $R_{eq(series)} = \sum_{k=1}^{n} R_{k}$ ) and in parallel ($R_{eq(parallel)} =\frac{1} { \sum_{k=1}^{n} \frac{1}{R_{k}} }$ )