Magnetic field patterns for a straight conductor

Magnetic field patterns for a straight conductor created by a current moving through a it forms concentric circles around the conductor. See the illustrations in figure below.

To investigate magnetic field patterns round straight conductor, you may need to set up apparatus similar to the following diagram.

we hold a card with a small hole at the center horizontally so that a conductor in a complete circuit is vertical. The Conductor pass through the hole such that the cardboard and the wire are perpendicular to each other.

We sprinkle Iron fillings on the cardboard, disturb gently after closing the switch, then allow them to settle after disturbance. When around to settle they form a pattern close to the one illustrated below. This pattern brings us closer to determining Magnetic Field patterns For a straight conductor.

if we are to represent that on a diagram, it should be circles around the conductor as shown.

This shows that iron fillings settles in concentric circles around the conductor becoming less significant as the distance from the conductor increases from the center of the circle horizontally.

Drawing magnetic patterns For a straight conductor using a compass.

All you need is to remove the iron fillings from the cardboard . Simply open the circuit and collect the iron fillings from the card. Then leave the setup as before with a compass on the cardboard as in figure below.

After closing the switch, note the direction of the compass needle. Now put a dot at the end of the needle and move the compass to start at the end before making a dot at the end of the needle. Move the compass so that it’s position begins at the dot and repeat the same procedure until you have circumnavigated the wire to make the pattern as shown.

You can repeat the above procedure by selecting another radius from the conductor and trace the compass needle pattern to see it’s pattern of turning as it moves around the conductor.

observations

Compass needle are aligned in a circle pointing in the clockwise direction as in the setup described above in all radius selected to study the pattern.

If we reverse direction of current by changing the battery polarity, the circles we plot would be pointing anticlockwise direction.

Explaining Magnetic field patterns for a straight conductor

Magnetic fields produced by a straight current carrying conductor forms a pattern of concentric circles around the conductor.

You can predict direction of the Magnetic Field patterns For a straight conductor using of Fleming’s-Right hand grip rule which states that:

If you grasp a conductor carrying current in the right hand with the thumb pointing along the wire in the direction of the convection current, then the fingers will encircle the conductor in the direction of the magnetic field.

our use of Fleming’s Right-hand grip rule is illustrated below.

you can also determine direction of the magnetic field around straight conductor by use of Maxwell’s corkscrew rule which states that:

If you drive a right-handed screw forward in the direction of the conventional current , then the direction of the rotation of the screw is the direction of the field lines.

The figure below illustrated Maxwell’s corkscrew rule:

when using the Maxwell’s corkscrew rule, you imagine fastening the screw if the current is getting in to paper and you imagine removing the screw when current is moving out of the paper.

Related Topics

• Magnetic effect of electric current
• Properties and principles of magnets
• Mutual Induction In electromagnetism
• An A.C. generator
• Magnetic fields
• Hans Christian Ørsted
• The Lenz’s law
• Factors affecting magnitude of the induced e.m.f
• Hans Oersted
• Calculus Integration
• Induced Electromotive force
• Magnetic effect to an electric current

References

• Secondary Physics Student’s Book Four. 3rd ed., Kenya Literature Bureau, 2012.
• Tom D., and Heather K. Cambridge IGCSE Physics. 3rd ed., Hodder Education, 2018.