10th Class Science Magnetic Effects of Electric Current Electromagnetic Induction

       Electromagnetic Induction

This concept was first introduced by Michael Faraday in 1831 when he discovered that magnet can be used to produced electric current. The production of electricity from magnetism is called electromagnetic induction. This can be demonstrated by moving the conducting wire between the poles of the magnet or by moving the magnet, or by keeping the conductor fixed and moving the magnet. A galvanometer is an instrument which can detect the presence of feeble current in the circuit. Take a galvanometer and connect in series with the circuit of the conducting wire and place it between the poles of the magnet. When the wire is stationary, no deflection in the galvanometer can be seen and as we move the wire between the poles of the magnet we see the deflection in the galvanometer.

          Fleming's Right Hand Rule

The direction of induced current produced by electromagnetic induction can be found by using Fleming Right Hand Rule. According to this rule, if we hold the thumb finger, the fore finger and the middle finger of our right hand at perpendicular direction to each other in such a way that, the fore finger points in the direction of magnetic field, the thumb finger points in the direction of motion of the conductor, then the middle finger will point in the direction of induced current.

Let us take a thick copper wire suspended freely from a support by the means of a flexible wire and the wire is free to move. The one end of the wire is placed between the poles of a horse shoe magnet and is connected to a current sources. When the current is switched on through the wire, we observe that the wire is deflected out of the horse shoe magnet. When we switch off the current it returns to the original position between the poles of the magnet. The direction of the current in the wire placed in a magnetic field is perpendicular to the direction of the current and perpendicular to the magnetic field. The direction of the force on the conductor placed between the magnetic field is given by Fleming left Hand rule. According to this rule: Hold the fore finger, middle finger and the thumb finger of your left hand at right angle to each other in such a way that the forefinger points in the direction of the magnetic field and the middle finger points in the direction of current, then the thumb will points in the direction of the force acting on the conductor.