6.4.1Chemical Reactions
The Motor Effect — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions
5 min read 4 parts Lesson 12 of 21 Unit quiz
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Section 1 of 4The Motor Effect
Motor effect
- Motor effect A current-carrying conductor placed in a magnetic field experiences a force, because the two magnetic fields interact.
Field from the wire
- Field from the wire The current produces its own circular magnetic field around the wire, which combines with the external field.
Stronger force
- Stronger force The force is greater when the current is larger, or when the external magnetic field is stronger.
Direction of the force
- Direction of the force The force is perpendicular to both the current direction and the external magnetic field direction.
Section 2 of 4A Simple DC Motor
1
A current flows through a rectangular coil, which is placed between the poles of a permanent magnet.
2
The motor effect produces opposite forces on the two sides of the coil, so the coil turns.
3
A split-ring commutator reverses the current direction every half turn, so the forces keep turning the coil in the same direction.
4
Increasing the current, using a stronger magnet or adding more turns to the coil increases the turning force.
Section 3 of 4Factors in the Motor
Factors in the Motor
Current
- Current A larger current gives a larger force on the conductor and a faster turning coil.
Field strength
- Field strength A stronger magnetic field gives a larger force on the conductor for the same current.
Number of turns
- Number of turns More turns of wire on the coil give a bigger total turning force for the same current.
Commutator
- Commutator Without a commutator the coil would only rock back and forth instead of rotating continuously.
Section 4 of 4Exam Checklist & Tips
6.4.1 – Key Points for the Exam
- Motor effect The force on a current-carrying conductor placed in a magnetic field.
- Commutator A split-ring that reverses the current in the coil each half turn.
- Turning force The force that causes the coil of a motor to rotate.
- Magnetic field A region in which a magnet or current experiences a force.
- Coil A loop or series of loops of wire, used in motors and generators.
Common Mistakes
- Saying the magnetic field of a permanent magnet is produced by the current in the coil.
- Forgetting the commutator, so the coil would only rock back and forth.
- Claiming the force acts along the wire rather than at right angles to it.
- Thinking the motor effect creates a current; it is the generator effect that induces current from motion.
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