Summary
Electromagnetic induction involves generating an electromotive force (e.m.f.) by changing the magnetic field around a conductor. This principle is used in various applications, such as motors and transformers.
- Right hand grip rule — used to determine the relationship between the current and the magnetic field based upon the rotational direction. Example: If the current is upwards, the magnetic field will run in an anticlockwise direction.
- Solenoid — a long coil of wire that generates a magnetic field when current passes through it. Example: The magnetic field outside the solenoid is similar to that of a bar magnet.
- Fleming’s left-hand rule — used to predict the direction of force, current, or fields in a current-carrying conductor. Example: The thumb indicates the motion of the object.
- Electromagnetic induction — the process of inducing an e.m.f. in a conductor by changing the magnetic field around it. Example: Moving a wire up and down between magnets induces a current.
- Transformer — a device that changes the voltage of an alternating current using coils of wire. Example: A step-up transformer increases voltage by having more turns on the secondary coil.
Exam Tips
Key Definitions to Remember
- Right hand grip rule
- Solenoid
- Fleming’s left-hand rule
- Electromagnetic induction
- Transformer
Common Confusions
- Direction of current and magnetic field using the right hand grip rule
- Difference between step-up and step-down transformers
Typical Exam Questions
- What is electromagnetic induction? It is the process of generating an e.m.f. by changing the magnetic field around a conductor.
- How does a transformer work? It changes the voltage of an alternating current using primary and secondary coils.
- What factors affect the magnitude of an induced e.m.f.? The rate of movement, strength of the magnet, and number of coils.
What Examiners Usually Test
- Application of Fleming’s left-hand rule
- Understanding of how transformers change voltage
- Factors affecting the strength of a magnetic field in a solenoid