Question

State the following laws with the help of labelled diagram. With the help of the following, the direction of which physical quantity can be known?
(i) Fleming’s Left Hand Rule
(ii) Right Hand Thumb Rule

Hint:

Remember: - Left hand → For electric motors (motion). - Right hand → For current-carrying conductors (magnetic field direction).

Answer 1

(i) Fleming’s Left Hand Rule:
When the thumb, forefinger, and middle finger of the left hand are stretched mutually perpendicular to each other: - The Forefinger points in the direction of the magnetic field (B).
- The Middle finger points in the direction of the current (I).
- The Thumb gives the direction of the force (motion) acting on the conductor.
This rule helps to determine the direction of the motion of a current-carrying conductor placed in a magnetic field.
Labelled Diagram (Fleming’s Left Hand Rule):
A simple diagram shows a left hand with the thumb, forefinger, and middle finger mutually perpendicular. \[ \text{Thumb → Force, Forefinger → Magnetic Field, Middle Finger → Current.} \] Physical Quantity Determined: Direction of force on the conductor.
(ii) Right Hand Thumb Rule:
If a current-carrying conductor is held in the right hand such that the thumb points in the direction of current, then the fingers encircling the wire give the direction of the magnetic field lines.
Labelled Diagram (Right Hand Thumb Rule):
A right hand gripping a straight conductor — thumb points in direction of current, and curved fingers show circular magnetic field lines around it.
Physical Quantity Determined: Direction of the magnetic field around a conductor.
Step 3: Conclusion.
Fleming’s Left Hand Rule is used to determine the direction of motion or force, while the Right Hand Thumb Rule is used to determine the direction of the magnetic field.