The magnitude of the magnetic field produced depends upon
- strength of current flowing in the conductor
- shape, size of conductor &
- position of observation point where the field is to be calculated.
Direction of magnetic field due to both straight as well as curved conductor can be calculated by right hand stretched thumb rule. For straight conductor thumb point current & curl of fingers point magnetic lines while in a curved conductor reverse of it. On reversing the direction of current the direction of magnetic field produced is reversed.