Lesson: Ohm’s Law Physics • 9th Grade

In this lesson, we will learn how to use the formula V = IR (Ohm’s Law) to work out the values of the potential difference, current, and resistance in simple circuits.

Lesson Plan

Objectives

Students will be able to

recall that ohms are the unit of electrical resistance,
use in all permutations,
state how the current through an ohmic conductor varies with potential difference across it,
state how the current through a filament bulb varies with potential difference across it,
state how the current through a diode varies with potential difference across it,
identify an ohmic conductor from a graph of its current and potential difference characteristics,
state how the resistance of an LDR varies with light incident upon it,
state how the resistance of a thermistor varies with temperature.

Prerequisites

Students should already be familiar with

what electric charge is,
what electric current is,
the units of charge and current,
the circuit symbols for a cell, a battery, a resistor, a bulb, a diode, an LED, an LDR, a thermistor, and a variable resistor.

Exclusions

Students will not cover

parallel circuits,
any kind of non-direct current,
Kirchhoff’s laws.

Lesson Video

Sample Question Videos

02:43
01:16
01:25

Lesson Worksheet

Q1:

A resistor in a circuit has a potential difference of 20 V across it. The current through the resistor is 0.4 mA. What is the resistance of the resistor?

Q2:

Which of the following is the correct unit for potential difference?

Q3:

How many volts are there in 20 kilovolts?