Summary
Electromagnetic induction involves generating an electromotive force (e.m.f.) through a changing magnetic field. It is used in devices like generators and transformers to convert and manage electrical energy.
- Faraday's Law — states that the magnitude of the induced e.m.f is proportional to the rate of change of magnetic flux through the circuit. Example: Increasing the speed of a magnet moving through a coil increases the induced e.m.f.
- Lenz's Law — states that the induced current is always in the direction that opposes the change producing it. Example: If a magnet is moved towards a coil, the induced current will create a magnetic field opposing the magnet's motion.
- Fleming's Right Hand Rule — used to determine the direction of induced current when a wire moves through a magnetic field. Example: If a wire moves downwards through a magnetic field pointing into the page, the current will flow to the right.
- A.C. Generator — a device that converts mechanical energy into alternating current using a rotating coil in a magnetic field. Example: As the coil rotates, it cuts through the magnetic field, inducing an alternating current.
- Transformer — a device that changes the voltage of an alternating current using two coils and a soft iron core. Example: A step-up transformer increases voltage for efficient power transmission.
Exam Tips
Key Definitions to Remember
- Faraday's Law: The induced e.m.f is proportional to the rate of change of magnetic flux.
- Lenz's Law: The induced current opposes the change causing it.
- Fleming's Right Hand Rule: Determines the direction of induced current.
Common Confusions
- Confusing Lenz's Law with Faraday's Law.
- Misapplying Fleming's Right Hand Rule by using the left hand.
Typical Exam Questions
- What is Faraday's Law? Faraday's Law states that the induced e.m.f is proportional to the rate of change of magnetic flux.
- How does an A.C. generator work? It converts mechanical energy into electrical energy by rotating a coil in a magnetic field.
- What is the function of a transformer? A transformer changes the voltage of an alternating current using two coils and a soft iron core.
What Examiners Usually Test
- Understanding and application of Faraday's and Lenz's Laws.
- Ability to describe and explain the operation of an A.C. generator.
- Calculations involving transformer equations and understanding of voltage transformations.