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Magnetic Field due to a Current Carrying Circular Loop

The demonstration given below explains the nature of magnetic field due to a current carrying circular loop.

magnetic field pattern around circular loop

Procedure Observation
Take a long wire and bend it to form a circle Concentric circles are formed, which are centred at the point where the wire passes through the cardboard
Pass the wire through the cardboard such that half the wire is above it and the remaining part of the wire is below the cardboard The lines near the centre of the loop are almost straight. The magnetic field at the centre of the loop is perpendicular to the plane of the loop
Join the free ends of the wire to a battery through a plug key The concentric circles become larger as we move away from the wire
Insert the key and pass the current. Sprinkle iron filings on the cardboard and tap gently
Note the pattern of the iron filings that emerge on the cardboard

magnetic field pattern around when reverse current in circular loop

Procedure Observation
Repeat the experiment by reversing the direction of flow of current The needle of the compass deflects in the opposite direction

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Procedure Observation
Repeat the experiment by increasing the strength of the current On increasing the strength of current in the conducting wire, the number of lines of force around it increases

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Procedure Observation
Repeat the experiment by increasing the number of turns of the coil The number of lines of force around the coil increases

magnetic field pattern around a circular loop of smaller radius

Procedure Observation
Repeat the experiment by reducing the radius of the coil The number of lines of force around the coil increases

Sub Topics
 

Inference

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The direction of magnetic field changes when the direction of flow of current is reversed

  • The strength of the magnetic field increases with increase in current

  • The strength of the magnetic field at the centre of a circular coil carrying current is proportional to the number of turns in the coil (n). As we increase the turns, the magnetic field strength also increases. As we go away from the wire, the strength of the magnetic field decreases, and the concentric circles grow larger in size

  • The strength of the magnetic field is inversely proportional to the radius of the circular coil i.e. the field strength reduces as the radius of the coil increases


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