Key relationship
ε=−N dΦ/dt; I=ε/R.
Physics · Class 12
Lenz law direction
The minus sign means the induced current creates a field opposing the change in flux. When increasing flux becomes decreasing flux, induced current reverses. Heating remains nonnegative.
Open the interactive experiment →Lenz law direction
லென்ஸ் விதியில் தூண்டிய மின்னோட்டம் பாய மாற்றத்தை எதிர்க்கும். பாய மாற்றம் மாறினால் மின்னோட்டம் திரும்பும்.
Key notes, relationships and model limits
Remember
The minus sign means the induced current creates a field opposing the change in flux. When increasing flux becomes decreasing flux, induced current reverses. Heating remains nonnegative.
Common trap
The induced response opposes the change in flux. It does not always oppose the original magnetic field itself.
Model limits
Sign convention: positive surface normal is along positive B; positive current would create positive flux. Fixed geometry and resistive loop.
What you will learn
Use the controls and plotted relation to explain lenz law direction.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
For N A=1 m²-turn and R=10 Ω, dB/dt=+0.5 gives I=−0.05 A; −0.5 gives +0.05 A.
Why this matters
The model connects lenz law direction with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
When an increasing positive flux is reversed to decreasing flux, induced current?
- Retains its original direction.
- Reverses direction.
- Becomes zero for every decreasing flux.
Read the explanation
Reverses direction.
Course connection: Class XII Chapter 6. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.