Magnetic Field Intensity

Description:

Intensity of magnetic field can be calculated by considering different scenarios in which a charge particle ‘q’ moving with a velocity ‘V’ in a magnetic field ‘B’ experiences a force ‘F’.

1. If we place a charge moving with a constant velocity in three different magnetic fields.

B₃ > B₂ > B₁

F₃ > F₂ > F₁

Hence force experienced by the charge is directly proportional to magnetic field.

F α B

2. If we place three different charges moving with the same velocity in a constant magnetic field.

q₃ > q₂ > q₁

F₃ > F₂ > F₁

Hence force experienced by the charge is directly proportional to magnitude of charge.

F α q

3. If we place a charge in the same magnetic field 3 times with a different velocity in each case.

V₃ > V₂ > V₁

F₃ > F₂ > F₁

Hence force experienced by the charge is directly proportional to velocity.

F α V

Therefore:

F α qVB

F = kqVB

Where k is a constant.

Intensity of magnetic field at any location is the force experienced by a unit charge, moving at right angle to the field with unit velocity.

I.e. q = 1, sinθ and V = 1

Therefore,

F = qVBsinθ = 1

B = F

Direction of force on charge is given by left hand rule.

Left Hand Rule

When a charge experiences a force by the magnetic field generated by a current carrying conductor the direction of force is given by left hand rule –

In left hand rule we need to place the index finger, middle finger and the thumb at right angle to each other.

Now place the index finger of the left hand along the magnetic field, middle finger in the direction of velocity of charge then the thumb will indicate the direction of the force on the charge.