There are two laws in electrical field for determining direction of three parameters Magnetic field, Current, & force.
If you know any of these two remaining parameter direction will be determined by Fleming rules. There are two Fleming rules:-
1. Fleming Left Hand rule
This rule is applicable for Electric Motors
2. Fleming Right Hand rule.
This rule is applicable for Electrical generators.
1. Fleming Left Hand rule:-
According to this law Whenever any current carrying conductor is placed in magnetic field then force is experienced on the conductor in a direction perpendicular to magnetic field and current.
Same is shown by Fleming left hand rule.
Now let’s take an example as shown below where a conductor having length “L” is placed in magnetic field having strength “H”. This magnetic field produces a current “I”. This magnitude of force which acts on conductor is as F= BIL
Now according to Fleming left hand rule, take three fingers forefinger, Second finger and Thumb all in right angle to each other. Now point fore-finger towards the direction of magnetic field, Second finger will points towards the direction of current then thumb will give the direction of force on conductor. Magnitude of the force on conductor will be = BIL
Where, B represents strength of Magnetic field.
2. Fleming Right Hand rule:-
According to Faraday's law of electromagnetic induction, whenever a conductor moves inside a magnetic field, there will be an induced current in it.
Now if a conductor forcefully moved inside the magnetic field, there will be a relation between the direction of applied force, magnetic field and the current. Then relation between Magnetic field force, Current and applied force will be given by Fleming right Hand rule.
Now according to Fleming right Hand rule Hold the first finger, Second finger and Thumb of your right hand all in right angle to each other. Then point forefinger towards line of force, then thumb will point towards direction of applied force and Second finger will give direction of current induced in conductor.