Olatunde Akanbi
Member
I’ve taught Ohm’s Law for many years, in good schools, average schools, crowded classes, and online classes. The biggest mistake teachers make is starting with the formula. The moment you write V = IR first, half the class switches off mentally. They start memorising instead of understanding.
Here’s how I would plan a 40-minute SS2 Ohm’s Law lesson, using simple language and real sense.
First, what is the mindset before I enter the class?
Your goal is not to make them remember the formula.
Your goal is to make them say, “Ahhh, so that’s why.”
If they understand the idea, the formula becomes easy later.
0–5 minutes: Start from what they know, not Physics.
I never announce “Today we’re doing Ohm’s Law”.
I start like this: “Have you noticed that when NEPA light is low, fan turns slowly, but when the light is strong, fan becomes fast?”
Let them answer. They always do.
Then I ask:
“Why doesn’t the fan always rotate at the same speed?”
Some will say:
• Light is weak
• Current is not enough
• Voltage is low (some bright students)
That’s enough.
Now I say:
“Today, we are going to understand why electricity behaves like that.”
No formula yet.
5–10 minutes: Use a strong everyday analogy
This is where experience matters.
I use water and pipe, because every Nigerian student understands it.
I draw three things on the board:
• A water tank
• A pipe
• A tap
Then I explain slowly:
• The pressure pushing water is like voltage
• The water flowing is like current
• The pipe size or blockage is like resistance
Then I say:
“If pressure is high, more water flows.”
“If pipe is small or blocked, water struggles.”
I pause and look at their faces.
If they’re nodding, you’re winning.
10–18 minutes: Introduce the idea of Ohm’s Law (still no formula)
Now I connect it back to electricity.
I say it in plain language:
“In an electric circuit, three things are connected:
Voltage pushes
Current flows
Resistance blocks”
Then the key sentence:
“The more the push, the more the flow.”
“The more the blockage, the less the flow.”
I repeat it twice in different ways.
Only after this do I say:
“This relationship is what we call Ohm’s Law.”
Still no formula.
18–25 minutes: Now introduce the formula gently
This is where many teachers rush. Don’t.
I write slowly:
V = IR
Then I say:
• V means how strong the push is
• I means how much electricity is flowing
• R means how hard the wire or device is blocking it
Then the most important part:
“This formula is just a short way of saying what we already understand.”
I rewrite it verbally:
Voltage = Current × Resistance
I show them:
• Increase voltage, current increases
• Increase resistance, current reduces
I ask simple oral questions:
• “If resistance is very big, will current be much or small?”
They answer. That’s how they learn.
25–33 minutes: Classroom examples (this is where students remember you)
I use phone charging, every single time.
Example 1: Phone charger
“Why does phone not charge fast when you use a bad charger or long cable?”
Explain:
• Cable has resistance
• More resistance, less current
• Less current, slow charging
Example 2: Electric pressing iron
“Why does iron have thick wire?”
Answer:
• High current
• Thick wire reduces resistance
• Prevents overheating
Example 3: Extension box
“Why do extension boxes sometimes get hot?”
Answer:
• Too many devices
• High current
• Resistance causes heat
At this point, students start giving their own examples. That’s success.
33–38 minutes: Very simple calculation (do not overdo it)
Only one example.
Example:
• V = 12 V
• R = 6 Ω
Ask them:
“What is the current?”
Solve it slowly:
I = V ÷ R
I = 12 ÷ 6
I = 2 A
No long maths. One example is enough for first lesson.
38–40 minutes: Close with understanding, not homework overload
I end with this sentence every time:
“Ohm’s Law is not a formula to cram.
It’s just telling us how electricity behaves”
Then quick recap:
• Voltage pushes
• Current flows
• Resistance blocks
Homework:
• Just 2 simple questions
• One theory, one calculation
Common mistakes I’ve made (so you don’t repeat them)
• Starting with V = IR immediately
• Giving too many calculations in one lesson
• Not using simple examples
• Teaching Ohm’s Law like maths instead of behaviour
Once I corrected these, student understanding improved drastically.
Final advice from experience
If students leave your class remembering:
• NEPA light example
• Water and pipe example
• Phone charger example
Then Ohm’s Law has entered their brains
Feel free to share
Here’s how I would plan a 40-minute SS2 Ohm’s Law lesson, using simple language and real sense.
First, what is the mindset before I enter the class?
Your goal is not to make them remember the formula.
Your goal is to make them say, “Ahhh, so that’s why.”
If they understand the idea, the formula becomes easy later.
0–5 minutes: Start from what they know, not Physics.
I never announce “Today we’re doing Ohm’s Law”.
I start like this: “Have you noticed that when NEPA light is low, fan turns slowly, but when the light is strong, fan becomes fast?”
Let them answer. They always do.
Then I ask:
“Why doesn’t the fan always rotate at the same speed?”
Some will say:
• Light is weak
• Current is not enough
• Voltage is low (some bright students)
That’s enough.
Now I say:
“Today, we are going to understand why electricity behaves like that.”
No formula yet.
5–10 minutes: Use a strong everyday analogy
This is where experience matters.
I use water and pipe, because every Nigerian student understands it.
I draw three things on the board:
• A water tank
• A pipe
• A tap
Then I explain slowly:
• The pressure pushing water is like voltage
• The water flowing is like current
• The pipe size or blockage is like resistance
Then I say:
“If pressure is high, more water flows.”
“If pipe is small or blocked, water struggles.”
I pause and look at their faces.
If they’re nodding, you’re winning.
10–18 minutes: Introduce the idea of Ohm’s Law (still no formula)
Now I connect it back to electricity.
I say it in plain language:
“In an electric circuit, three things are connected:
Voltage pushes
Current flows
Resistance blocks”
Then the key sentence:
“The more the push, the more the flow.”
“The more the blockage, the less the flow.”
I repeat it twice in different ways.
Only after this do I say:
“This relationship is what we call Ohm’s Law.”
Still no formula.
18–25 minutes: Now introduce the formula gently
This is where many teachers rush. Don’t.
I write slowly:
V = IR
Then I say:
• V means how strong the push is
• I means how much electricity is flowing
• R means how hard the wire or device is blocking it
Then the most important part:
“This formula is just a short way of saying what we already understand.”
I rewrite it verbally:
Voltage = Current × Resistance
I show them:
• Increase voltage, current increases
• Increase resistance, current reduces
I ask simple oral questions:
• “If resistance is very big, will current be much or small?”
They answer. That’s how they learn.
25–33 minutes: Classroom examples (this is where students remember you)
I use phone charging, every single time.
Example 1: Phone charger
“Why does phone not charge fast when you use a bad charger or long cable?”
Explain:
• Cable has resistance
• More resistance, less current
• Less current, slow charging
Example 2: Electric pressing iron
“Why does iron have thick wire?”
Answer:
• High current
• Thick wire reduces resistance
• Prevents overheating
Example 3: Extension box
“Why do extension boxes sometimes get hot?”
Answer:
• Too many devices
• High current
• Resistance causes heat
At this point, students start giving their own examples. That’s success.
33–38 minutes: Very simple calculation (do not overdo it)
Only one example.
Example:
• V = 12 V
• R = 6 Ω
Ask them:
“What is the current?”
Solve it slowly:
I = V ÷ R
I = 12 ÷ 6
I = 2 A
No long maths. One example is enough for first lesson.
38–40 minutes: Close with understanding, not homework overload
I end with this sentence every time:
“Ohm’s Law is not a formula to cram.
It’s just telling us how electricity behaves”
Then quick recap:
• Voltage pushes
• Current flows
• Resistance blocks
Homework:
• Just 2 simple questions
• One theory, one calculation
Common mistakes I’ve made (so you don’t repeat them)
• Starting with V = IR immediately
• Giving too many calculations in one lesson
• Not using simple examples
• Teaching Ohm’s Law like maths instead of behaviour
Once I corrected these, student understanding improved drastically.
Final advice from experience
If students leave your class remembering:
• NEPA light example
• Water and pipe example
• Phone charger example
Then Ohm’s Law has entered their brains
Feel free to share