Key relationship
Bwire=µ₀I/(2πr).
Physics · Class 12
Oersted current and compass
A current produces magnetic field circles around a straight wire. Reversing current reverses circulation and compass deflection; the right-hand rule gives direction.
Open the interactive experiment →Oersted current and compass
மின்னோட்டக் கம்பியைச் சுற்றி காந்தப்புலம் உருவாகிறது. மின்னோட்டத் திசை மாறினால் காந்தப்புலத் திசையும் மாறும்.
Key notes, relationships and model limits
Remember
A current produces magnetic field circles around a straight wire. Reversing current reverses circulation and compass deflection; the right-hand rule gives direction.
Common trap
Use the right-hand rule for conventional current; reversing current reverses the wire’s circular magnetic field.
Model limits
Ideal long wire when selected; compass torque follows field direction, and the graph uses signed circulation.
What you will learn
Use the controls and plotted relation to explain oersted current and compass.
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
At I=2 A and r=0.1 m, a long wire produces B=4 µT.
Why this matters
The model connects oersted current and compass with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
Reversing a wire current does what to its magnetic field?
- Only halves its magnitude.
- Reverses the magnetic-field direction.
- Leaves both magnitude and direction unchanged.
Read the explanation
Reverses the magnetic-field direction.
Course connection: Class XII Chapter 4. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.