To observe the magnetic field lines around current carrying conductor.
- Magnetic effect of electric current is one of the major effects of electric current in use, without the applications of which we cannot have motors in the existing world.
- A current carrying conductor creates a magnetic field around it, which can be comprehended by using magnetic lines of force or magnetic field lines.
- The nature of the magnetic field lines around a straight current carrying conductor is concentric circles with centre at the axis of the conductor.
- The strength of the magnetic field created depends on the current through the conductor.
- The direction of the magnetic field lines of force around a conductor is given by the Maxwell’s right hand grip rule or the right handed corkscrew rule. Imagine that you are holding a current-carrying straight conductor in your right hand such that the thumb points towards the direction of current. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field (See Fig.1). This is known as right hand thumb rule.
Fig 1 - Right hand thumb rule.
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.
- Fix the cardboard and insert the wire through the centre of cardboard such that it is normal to its plane.
- Connect the wire with rheostat, ammeter, battery and plug key in series.
- Sprinkle the iron filings uniformly on the cardboard.
- Keep the variable of the rheostat at a fixed position and note the current through the ammeter.
- Close the key and gently tap the cardboard.
- Observe the pattern of the iron filings over the cardboard.
As performed in the simulator
- Adjust the current flowing from the conductor and distance of the object from the conductor using the sliders from the Controls section.
- Note the direction of the magnetic field and also the direction of current flowing through the conductor.
- Also, note the magnetic field (B) acting on the object O.
- Click on "Change Current Direction" checkbox, to change the direction of current.
- Click on "Observations " tab below to view the observation.
- 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.
- The direction of the field is perpendicular to the conductor.
- The magnetic field (B) acting on the object O increases as the current flowing through it increases.
- The field increases as object O is closer to the conductor and decreases as it moves away from the conductor.
- The direction of magnetic field lines gets reversed if the direction of current is reversed.