Summary
When a current-carrying conductor is placed in a magnetic field, it experiences a force at right angles to both the current and the field. This force can be predicted using Fleming's left-hand rule and is influenced by factors such as the strength of the magnetic field, the current, and the length of the wire in the field.
- Fleming's Left-Hand Rule — used to predict the direction of force on a current-carrying conductor in a magnetic field. Example: Thumb indicates motion, first finger indicates magnetic field direction, and second finger indicates current direction.
- Turning Effect — the force that causes a coil in a magnetic field to turn when a current passes through it. Example: Increasing the number of turns on the coil, the current, or the strength of the magnetic field increases the turning effect.
- Commutator — a device that reverses the direction of current in a coil every half turn to keep it spinning. Example: Used in D.C. motors to maintain continuous rotation.
Exam Tips
Key Definitions to Remember
- Fleming's Left-Hand Rule
- Turning Effect
- Commutator
Common Confusions
- Direction of force using Fleming's left-hand rule
- Effect of reversing current direction on magnetic field polarity
Typical Exam Questions
- What happens to a wire carrying a current in a magnetic field? It experiences a force at right angles to both the current and the field.
- How can the turning effect on a coil be increased? By increasing the number of turns, the current, or the strength of the magnetic field.
- What is the role of a commutator in a D.C. motor? It reverses the direction of current every half turn to keep the coil spinning.
What Examiners Usually Test
- Application of Fleming's left-hand rule
- Factors affecting the force on a current-carrying conductor
- Understanding of how a D.C. motor operates