Magnetic field lines around current carrying conductor

As performed in the real lab


A battery (12 V), a variable resistance (or a rheostat), an ammeter (0–5 A), a plug key, and a long straight thick copper wire.


  1. Fix the cardboard and insert the wire through the centre of cardboard such that it is normal to its plane.
  2. Connect the wire with rheostat, ammeter, battery and plug key in series.
  3. Sprinkle the iron filings uniformly on the cardboard.
  4. Keep the variable of the rheostat at a fixed position and note the current through the ammeter.
  5. Close the key and gently tap the cardboard.
  6. Observe the pattern of the iron filings over the cardboard.

As performed in the simulator

  1. Adjust the current flowing from the conductor and distance of the object from the conductor using the sliders from the Controls section.
  2. Note the direction of the magnetic field and also the direction of current flowing through the conductor.
  3. Also, note the magnetic field (B) acting on the object O.
  4. Click on "Change Current Direction" checkbox, to change the direction of current.
  5. Click on "Observations " tab below to view the observation.


  1. You will observe that the magnetic field lines are formed in concentric circles around the current carrying conductor. These lines do not intersect each other and are equidistant from each other.
  2. The direction of the field is perpendicular to the conductor.
  3. The magnetic field (B) acting on the object O increases as the current flowing through it increases.
  4. The field increases as object O is closer to the conductor and decreases as it moves away from the conductor.
  5. The direction of magnetic field lines gets reversed if the direction of current is reversed.