Moving Charges And Magnetism; memorizing tricks

 

Moving Charges And Magnetism

- Finding difficulties in ? Let us learn it in some easy ways

1

Direction of Magnetic Force

Whenever a charged particle with charge q and velocity v enters a region with field B it experiences a force given by

F=q[v×B]

The direction of the force is given by the right hand thumb rule or the curl rule

There is a second right hand rule that shows the direction of the force on a positive charge in a magnetic field. Point your index finger along the direction of the particle's velocity. If your middle finger points along the magnetic field, your thumb will point in the direction of the force. NOTE: For negative charge reverse the direction of the force (or use your left hand).

2

Direction of Magnetic Field-Biot Savart's Law

According to Biot Savart's Law, the field due to a current element dl carrying current I at a distance r is given by

dB=4πμo​​r3Idl×r​

Let us determine an easy way to determine the direction of magnetic field dB in a simple way, or should we say ways.

• The direction of field is given by the direction of vector product of Idl×r.The direction of vector product can be easily found by the right hand rule.

3

Right Hand Thumb Rule or Curl Rule: If a current carrying conductor is imagined to be held in the right hand such that the thumb points in the direction of the current, then the tips of the fingers encircling the conductor will give the direction of the magnetic lines of force.