Lesson Plan
Ohm's Law: Power Up!
Students will be able to define Ohm's Law and confidently calculate voltage, current, and resistance using the formula V=IR.
Understanding Ohm's Law is fundamental to comprehending how electrical circuits work in everyday devices, from your phone charger to household appliances. This lesson provides practical skills for analyzing and solving real-world electrical problems.
Audience
10th Grade Students
Time
30 minutes
Approach
Interactive lecture and guided practice.
Prep
Prepare Materials
10 minutes
- Review the Ohm's Law Power Up! Slide Deck and familiarize yourself with the content.
- Print copies of the Ohm's Law Practice Problems Worksheet for each student.
- Have the Ohm's Law Practice Problems Answer Key ready for quick reference during class discussion.
Step 1
Introduction & Warm-Up
5 minutes
- Begin with a quick question to gauge prior knowledge about electricity or circuits. (e.g., "What do you think happens when you plug something into an outlet?")
- Introduce the lesson title, "Ohm's Law: Power Up!" and briefly explain its importance.
- Transition to the Ohm's Law Power Up! Slide Deck for the main instruction.
Step 2
Ohm's Law Explained
10 minutes
- Present slides 1-4 from the Ohm's Law Power Up! Slide Deck.
- Clearly define Voltage, Current, and Resistance.
- Introduce Ohm's Law: V = IR.
- Provide one or two simple examples of calculations, explaining each step clearly.
- Encourage questions and check for understanding before moving on.
Step 3
Guided Practice
10 minutes
- Distribute the Ohm's Law Practice Problems Worksheet.
- Work through the first problem or two on the worksheet together as a class, guiding students through the process.
- Allow students to work independently or in pairs on the remaining problems.
- Circulate around the room to offer support and answer individual questions.
Step 4
Review & Cool-Down
5 minutes
- Bring the class back together.
- Review the answers to the Ohm's Law Practice Problems Worksheet using the Ohm's Law Practice Problems Answer Key, allowing students to self-correct.
- Address any common misconceptions or challenging problems.
- Conclude with a brief summary of why Ohm's Law is important.
Slide Deck
Ohm's Law: Power Up!
Understanding Electricity's Rules!
Welcome students and kick off with an engaging question to activate prior knowledge. Relate electricity to their daily lives.
The Big Three: V, I, R
Voltage (V): The 'push' that makes electricity move. Measured in Volts.
Current (I): The 'flow' of electricity. Measured in Amperes (Amps).
Resistance (R): The 'opposition' to electricity's flow. Measured in Ohms (Ω).
Introduce the three key terms. Emphasize that these are the building blocks for understanding circuits. Use simple analogies if helpful (e.g., voltage as 'push', current as 'flow', resistance as 'bottleneck').
Ohm's Law: The Formula!
Ohm's Law shows how Voltage, Current, and Resistance are connected:
V = I × R
Where:
- V = Voltage (Volts)
- I = Current (Amps)
- R = Resistance (Ohms, Ω)
Think of it like a river: - Voltage is the steepness of the riverbed (how much 'push' the water has).
- Current is how much water flows past a point (the amount of flow).
- Resistance is how narrow or rocky the riverbed is (how much it slows the water down).
Introduce Ohm's Law as the relationship between V, I, and R. Clearly state the formula. Explain the Ohm's Law triangle as a mnemonic device for rearranging the formula.
Let's Calculate! (Example 1)
Problem: A circuit has a resistance of 10 Ω and a current of 2 A flowing through it. What is the voltage across the circuit?
Given:
- R = 10 Ω
- I = 2 A
Formula: V = I × R
Calculation:
- V = 2 A × 10 Ω
- V = 20 Volts
Answer: The voltage across the circuit is 20 Volts.
Work through a simple example problem step-by-step. Show how to identify the knowns and unknowns, choose the correct formula, and perform the calculation. Emphasize units.
Let's Calculate! (Example 2)
Problem: A 12 V battery powers a light bulb with a resistance of 4 Ω. What is the current flowing through the bulb?
Given:
- V = 12 V
- R = 4 Ω
Formula: I = V / R
Calculation:
- I = 12 V / 4 Ω
- I = 3 Amperes
Answer: The current flowing through the bulb is 3 Amperes.
Provide another example, this time solving for current. Again, guide students through the steps. This prepares them for the worksheet.
Time to Practice!
Now it's your turn to apply Ohm's Law!
Work through the problems on your worksheet. Remember to:
- Identify what you know and what you need to find.
- Choose the correct formula (V=IR, I=V/R, or R=V/I).
- Show your work!
- Include the correct units in your answer.
Don't be afraid to ask questions!
Introduce the worksheet and explain that students will now apply what they've learned. Reiterate that they can work together or ask questions.
Worksheet
Ohm's Law Practice Problems
Instructions: Read each problem carefully, identify the known values, choose the correct Ohm's Law formula (V=IR, I=V/R, or R=V/I), show your work, and write your final answer with the correct units.
Problems
-
A flashlight bulb has a resistance of 3 Ohms. If the flashlight uses two 1.5 Volt batteries (for a total of 3 Volts), what is the current flowing through the bulb?
-
An electric heater draws a current of 10 Amperes when connected to a 120 Volt power supply. What is the resistance of the heater?
-
If a circuit has a resistor with 50 Ohms of resistance and a current of 0.5 Amperes flowing through it, what is the voltage across the resistor?
-
A car headlight bulb has a resistance of 6 Ohms. If the car battery supplies 12 Volts, what is the current passing through the headlight?
-
You have an unknown resistor in a circuit. When you apply 9 Volts across it, a current of 0.03 Amperes flows through. What is the resistance of the unknown resistor?
-
A small motor has a resistance of 24 Ohms. If 0.25 Amperes of current run through the motor, what is the voltage required to operate it?
Answer Key
Ohm's Law Practice Problems Answer Key
Instructions: Review the solutions below to check your work and understand the correct application of Ohm's Law.
Solutions
-
A flashlight bulb has a resistance of 3 Ohms. If the flashlight uses two 1.5 Volt batteries (for a total of 3 Volts), what is the current flowing through the bulb?
- Given: V = 3 V, R = 3 Ω
- Formula: I = V / R
- Calculation: I = 3 V / 3 Ω = 1 A
- Answer: The current flowing through the bulb is 1 Ampere.
-
An electric heater draws a current of 10 Amperes when connected to a 120 Volt power supply. What is the resistance of the heater?
- Given: V = 120 V, I = 10 A
- Formula: R = V / I
- Calculation: R = 120 V / 10 A = 12 Ω
- Answer: The resistance of the heater is 12 Ohms.
-
If a circuit has a resistor with 50 Ohms of resistance and a current of 0.5 Amperes flowing through it, what is the voltage across the resistor?
- Given: I = 0.5 A, R = 50 Ω
- Formula: V = I × R
- Calculation: V = 0.5 A × 50 Ω = 25 V
- Answer: The voltage across the resistor is 25 Volts.
-
A car headlight bulb has a resistance of 6 Ohms. If the car battery supplies 12 Volts, what is the current passing through the headlight?
- Given: V = 12 V, R = 6 Ω
- Formula: I = V / R
- Calculation: I = 12 V / 6 Ω = 2 A
- Answer: The current passing through the headlight is 2 Amperes.
-
You have an unknown resistor in a circuit. When you apply 9 Volts across it, a current of 0.03 Amperes flows through. What is the resistance of the unknown resistor?
- Given: V = 9 V, I = 0.03 A
- Formula: R = V / I
- Calculation: R = 9 V / 0.03 A = 300 Ω
- Answer: The resistance of the unknown resistor is 300 Ohms.
-
A small motor has a resistance of 24 Ohms. If 0.25 Amperes of current run through the motor, what is the voltage required to operate it?
- Given: I = 0.25 A, R = 24 Ω
- Formula: V = I × R
- Calculation: V = 0.25 A × 24 Ω = 6 V
- Answer: The voltage required to operate the motor is 6 Volts.