PhysicsChapter 10: Electromagnetism
Fleming Rules and Field Around A Wire
A current-carrying wire has a circular magnetic field (right-hand grip: thumb in conventional current, fingers show field).
Definition
A current-carrying wire has a circular magnetic field (right-hand grip: thumb in conventional current, fingers show field). Fleming left-hand rule gives the force on a current in a field (motor). Fleming right-hand rule gives the induced current direction (generator). Do not mix the hands.
Relationship
- left = motor
- right = generator
Overview
Two hands, two jobs:
Motor (left)
First finger Field, seCond finger Current, thuMb Motion. That is the force on a wire in a magnetic field (F = B I L for a school straight wire at 90 deg). A coil in a field becomes a motor if current is fed through a commutator.
Examples Loudspeaker coil (named) · Simple d.c. motor kit · Force is zero if I is parallel to B
Generator (right)
Move a conductor across a field and an emf appears (Faraday). Right-hand rule: Motion, Field, induced Current. Lenz: the induced current fights the change. A.c. generator uses slip rings; d.c. dynamo uses a commutator.
Examples Bicycle dynamo (named) · Moving a magnet into a coil · Transformers need changing flux, not a spinning hand on d.c.
Explanation
A long straight wire: field circles. A solenoid: field like a bar magnet, with a N and S. Increasing turns or current strengthens it. A core of iron concentrates the field (electromagnet, already in Class 9).
In simple words
Left-hand motor, right-hand dynamo. Writing the wrong hand loses the direction mark even if F = BIL is quoted.
Key points
- grip for the wire field
- left = motor
- right = generator
- F B I L
- commutator in a d.c. motor
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Fleming Rules and Field Around A Wire
Sticky Notes · Quick Revision
Core Idea
- A current-carrying wire has a circular magnetic field (right-hand grip: thumb in conventional current, fingers show field).
Key Points
- grip for the wire field
- left = motor
- right = generator
Simple Check
- Explain fleming rules and field around a wire in your own words and connect it to one chapter example.
How to Answer
- Define the idea, show the main rule or evidence, apply it, and check the final statement.
Common Mistake
- Left-hand motor, right-hand dynamo. Writing the wrong hand loses the direction mark even if F = BIL is quoted.
FBISE Exam Tip
- Use the exact term, show working where needed, and include units or labelled evidence.
60-second revision
- grip for the wire field
- left = motor
- right = generator
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