SS3 First Term Physics Lesson Note – Electromagnetic Field II

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ELECTROMAGNETIC FIELD II

CONTENT

• Electromagnetic field
• Fleming left hand rule
• Applications of electromagnetic field

ELECTROMAGNETIC FIELD:  This is a field representing the joint interaction of electric and magnetic forces.  It is exerted on charged particles.  The force on a charge q moving with velocity v less than the velocity of light is given by

F = q (E + v x B)

A conductor carrying an electric current when placed in a magnetic field experiences a mechanical force. It can be demonstrated by using two metal rails fixed on each side of a powerful horse-shoe magnet.  A copper rod is placed across the rails.   When we pass current through this copper rod, it is observed that the copper rood rolls along the rails, towards the right.  If by adjusting the rheostat, we cause more current to flow through the rod, we will observe that the rod moves faster. Thus, the force on the rod increases when the current increases.

Direction of the force – The direction of force on a current carrying conductor placed perpendicular to the magnetic field is given by Fleming’s left-hand rule which is stated as follows:

If the thumb, forefinger and middle finger are held mutually at right angles to one another with the fore-finger pointing in the direction of magnetic field, and the second finger in the direction of Current, then the thumb will point in the direction of the force producing motion.

APPLICATIONS OF ELECTROMAGNETIC FIELD

1.Electric Motor – The electric motor is a device for converting electrical energy into chemical energy.  It consists:

(i) A rectangular coil of insulated wire, known as armature

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