Fleming's left-hand rule
- CBSE · NCERT Class 10, Ch 12 Magnetic Effects of Electric Current
Fleming's left-hand rule gives the direction of the force on a current-carrying conductor placed at right angles to a magnetic field.
A wire carrying current inside a magnetic field feels a push. The push is largest when the current is at right angles to the field. To find its direction, hold the thumb, first finger and middle finger of your left hand at right angles to each other.
- First finger: the direction of the magnetic field.
- Middle finger: the direction of the current.
- Thumb: the direction of the force, or motion, of the conductor.
Reverse the current or the field, and the force reverses. The rule uses the left hand. The right-hand thumb rule answers a different question: the direction of the field around a wire.
A small example
A wire runs east to west, and a current of 3 A flows east in it. A magnet's field points north. First finger north, middle finger east: the thumb points up. So the wire is pushed upward. Reverse the current to flow west, and the push is downward.
Where marks go
CBSE's 2026-27 Science sample paper has no question on this rule. A marking scheme rewards the direction and the reasoning behind it. Watch for a beam of electrons given in place of a current.
Electrons move opposite to the current. So the middle finger must point against the beam's motion before the rule is applied. The answer then needs that reasoning written out, since step marking marks the working as well as the direction.
Sources
Facts last checked against these sources on 30 September 2026.
About the author
Founder Member & Academic Lead
An IIT alumna (M.Sc., M.Phil.) with over 25 years in teaching, child psychology and learning assessment. As Academic Lead at EduBrahma, she leads the method TRUtesting uses to find where and why a child loses marks.
Deepti Sardana on LinkedIn
