6 (a)], we have
p =   v||T  =  2pm v|| / q B
[4 6(b)]
The radius of the circular component of motion is called the radius of
the helix 4 4
MAGNETIC FIELD DUE TO A CURRENT ELEMENT,
BIOT-SAVART LAW
All magnetic fields that we know are due to currents (or moving
charges) and due to intrinsic magnetic moments of particles