Maxwell’s Right Hand Thumb Rule : Magnetic Effects of Electric Current

The magnetic effect of current was discovered by Hans Christian Oersted in 1820.

  • He found that a wire carrying current was able to deflect a compass needle.
  • As it was concluded that a current flowing in a wire always give rise to a magnetic field around it. it ultimately gives to rise to  mechanical force(when deflecting the needle)
  • Devices such as Electric Motor,Generator, TV , radio sets use the magnetic effect of current.

Experiment to demonstrate the magnetic effect of current

  • Make a simple electric circuit by joining a long straight wire with a battery and a plug.
  • Now, take a magnetic compass needle and place the straight wire parallel and over the compass needle.
  • Then switch on the circuit so that current flows through the wire from south to north directions.
  • Now, you will find that the north pole of compass needle gets deflected towards the west.

Image result for Experiment to demonstrate the magnetic effect of current

  • But, if the direction of current in the wire is reversed then the north pole of the compass needle gets deflected towards the east.

The direction of deflection of magnetic needle can be easily determined by SNOW rule.

  • According to SNOW rule, when current flows through a conductor from South to North direction and the wire is held over magnetic needle then the north pole of the magnetic needle deflects towards west.

Magnetic Field Patterns produced By Current carrying conductors having different shapes

we will study the patterns produced by various current carrying conductors having different shapes

  1. A straight conductor or straight wire carrying current
  2. A circular loop carrying  current
  3. A solenoid or long coil carrying current

  1. Magnetic field pattern produced by a straight current carrying conductor (straight current carrying wire)

Procedure

  • Take A vertical straight copper wire.
  • Pass the copper wire through a card board paper
  • Connect the ends of the wire to a battery
  • Take a Magnetic compass
  • Pass electricity through the wires by connecting the wires to a battery

Observation-

  • You will observe that the magnetic compass will deflect in anticlockwise direction
  • Now change the direction of passing current
  • This shows that magnetic field lines are circular in nature.

Now change the Direction of the flowing current by reversing the battery polarity.

you will observe that the magnetic field lines also gets reversed

The magnitude of magnetic field produced by a straight current carrying wire is

  • Directly proportional to current passing in the wire
  • Inversely proportional to the distance of the point from the wire

Direction of magnetic field produced by straight current carrying wire can be shown by Right Hand Thumb Rule

Maxwell’s Right Hand Thumb Rule

  • Imagine you are holding a current carrying wire in your right hand.so that the thumb points in the direction of the current,then the direction in which your finger encircle the wire will give the direction of the magnetic field lines around the wire

Maxwell’s right hand thumb rule is also known as Maxwell corkscrew rule.

  • Imagine you are driving a cork screw in the direction of the current then the direction in which you will turn the handle is the direction of the magnetic field.
  • Thus we can conclude that when electric current is flown vertically upwards the direction of magnetic field produced will be Anti-clock-wise
  • when the direction of the current is downwards then the magnetic field will be clock wise
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