Question

In the statement of Fleming's left-hand rule, magnetic field is represented by
A. Thumb
B. Fore finger
C. Middle finger
D. None

Answer 1

Fleming's left-hand rule is used to determine the direction of the force acting on a conductor which is placed in an external magnetic field and the conductor is also having a flowing current through it. By using this we can get the idea of mutual directions of the current flowing through the conductor, magnetic field and the force acting on the conductor or the direction of the motion of the conductor.

Complete answer:
Fleming's left hand rule states that if we stretch the thumb, fore finger and the middle finger of our left-hand such that they are mutually perpendicular to each other, and if the fore-finger is in the direction of the external magnetic field and middle-finger is in the direction of the current flowing through the conductor then the thumb will give the direction of the force acting on the conductor or the direction of the motion of the conductor.

Hence following is the list depicting the finger representing their respective quantity-
1. Fore finger- magnetic field
2. Middle finger- current
3. Thumb – force or the direction of the motion.
Hence in the statement of Fleming's left-hand rule, the magnetic field is represented by the fore finger of the left hand.

So, the correct answer is “Option B”.

Note:
Fleming's left-hand rule is only applicable for the conductors having a current which is generated by a battery or other source of energy, but this role is not applicable for the induced current. That means it cannot be use for the generators. So, for the generators we use Fleming's right hand rule which shows the direction of the induced current in the windings of the generators when a conductor which is already connected to the circuit and moving in a magnetic field.