Right Hand Thumb Rule
The right hand thumb rule is a rule used to find the direction of the magnetic field around a straight current-carrying conductor.
Practice This ConceptMain explanation
Teacher explanation
Hold the conductor in your right hand with the thumb pointing in the direction of current. The curled fingers then show the direction of the magnetic field lines around the wire. This rule is very useful because the magnetic field around a straight wire is circular, and the direction changes with current direction. Students should use the right hand, not the left hand, for this rule.
Example
If current flows upward in a straight wire, the curled fingers show the magnetic field direction around the wire in circles.
Simple analogy
Thumb for current, fingers for field.
Common confusion
A common mistake is using the left hand or confusing the thumb direction with the magnetic field direction.
Exam tip
In a short-answer question, mention the thumb for current and the curled fingers for magnetic field direction.
Answer writing and exam use
1-mark use
Write the exact meaning of right hand thumb rule in one clean line.
2-mark use
Define right hand thumb rule and add one example or condition.
3-mark use
Explain right hand thumb rule, show the method or example, and mention the common mistake.
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