Question

Which rule is used to find direction of magnetic field around current carrying conductors?
(a) Right Hand Thumb Rule
(b) Left Hand Thumb Rule
(c) Fleming's Right Hand Rule
(d) Fleming's Left Hand Rule

Answer 1

Hint – In this question use the concept that Fleming’s left hand rule helps establish relations between directions of magnetic field, force and current. The basics of Fleming’s left hand rule will help establish approaching the right solution for this problem.

Complete step-by-step answer:

Fleming’s left hand rule –
Whenever a current carrying conductor is placed in a magnetic field, it experiences a force due to the magnetic field. The direction of force acting on the conductor can be found using Fleming's Left Hand Rule. The middle finger points in the direction of the current, thumb points in the direction of force and index finger points in the direction of magnetic field as shown in the figure.
All the lines are at right angles to each other (i.e. at 90 degree w.r.t each other) as shown in the figure.
So we find out the direction of force due to magnetic induction.
So when the direction of the current is in the positive direction of the x-axis so according to Fleming’s left hand rule the direction of the magnetic field is in the positive direction of y-axis.
And if the direction of the current is in the positive direction of the y-axis so according to Fleming’s left hand rule the direction of the magnetic field is in the negative direction of x-axis.
And if the direction of the current is in the positive direction of the z-axis so according to Fleming’s left hand rule the direction of the magnetic field is in the positive direction of the y-axis.
So this is the required answer.
Hence option (D) is the right answer.

Note – The basic application of Fleming’s left hand rule is that it is used in electric motors since in electric motors the electric current exists the magnetic field so this results in production of a force, and it’s this force which is responsible for production of motion within the motor, this force provides an additional torque which helps in rotation of the motor.