Home Science Facrtor Magnetic Field

Factors On which the strength of the magnetic field inside a current carrying solenoid depends

  • The strength of the magnetic field is directly proportional to the amount of current flowing through the conductor.
  • Directly proportional to the nature of core substance present inside the solenoid.

Force on a current carrying conduction placed in a magnetic field

F = BIl sin 0

where

B = magnitude of magnetic field strength

I = Amount of current flowing through the conductor

L=Length of the conductor

0 = The angle between the direction of electric current and direction of magnetic field.

Case I

Current flows parallel to direction of magnetic field.

Q : Name the rule which will determine the direction of force in a current carrying conductor placed inside magnetic field.

Answer : Fleming left hand rule

When the fore finger , middle finger and thumb of your left hand such that they will be mutually perpendicular to each other. If the fore finger points in the direction of magnetic field and the middle finger shows the direction of current, then the thumb will show force on the conductor or direction of motion of conductor.

Electric motor

Construction and Working

  • Armature is a group of conducting wire in the shape of rectangle placed between two poles of a magnet. The armature can move around an axle.
  • Split ring type commutator – It consists of 2 halves of ring which are always in contains with carbon brushes r1 and r2.These ring can rotate around the axle along with the armature. These r1 and r2 are also connected to the armature.

Brushes

Two carbon brushes present in the electric motor are joined to the 2 terminals of the battery. The current can flow through the armature via brushes.

Strong Magnet

A horse-shoe magnet is present within which the armature will rotate. The magnet will provide the necessary magnetic filed.

Battery

A battery is connected to the provide necessary electricity.

Working

It can be noticed that the current gets flowing from the battery to the armature via brushes.

The current is flowing from A to B in the arm AB and From C to D in arm CD. By applying fleming’s left hand rule the AB arm goes downward and CD in downward. This way the armature will make a half rotation.

In the next half current flows in the direction DCBA. According to flemimg’s left hand rule, DC arm will go downward and AB arm goes upward. In this way there is complete rotation and armature will continuously move around the armature.