Electromagnets and electromagnetic induction Flashcards
What are 3 applications of an electromagnet?
A crane that picks up metal.
A relay switch
A circuit breaker
How can you increase the force exerted by an electromagnet?
Add more coils
Add more current
Add an iron core
What is electromagnetic induction?
The creation of P.d across a wire that is experiencing a change in magnetic field
How can you perform electromagnetic induction?
> move a magnet through a coil of wire
> move an electrical conductor through a magnetic field
How can you induce a current using a magnetic field?
> as you move the magnet, the magnetic field through a the cool changes, this change in magnetic field
induces a potential difference across the circuit, which can cause a current to flow through the coil.
How can you induce an alternating current?
> have a magnet on a pivot inside a coil of wire
> as you turn the magnet through a half turn the polarity reverses, this causes the voltage created to be reversed, causing the current to flow in the opposite direction through the coil
> if the magnet keeps turning in the same direction, the polarity will be reversed every half turn, causing the voltage to be reversed and creating an alternating current.
How does a transformer work?
> an alternating current is supplied to the insulated primary coil,
- this produces a CHANGING magnetic field in a the iron core, which produces a changing magnetic field in the secondary coil.
This induces an alternating P.d in the secondary coil ( with the same frequency as the primary coil)
> so an alternating current flows.
What is a switch mode transformer?
A transformer that operates at higher frequencies than traditional transformers.
> 50-200 kHz
Why can switch mode transformers be made lighter and smaller?
> because they operate at far higher frequencies
Why are switch mode transformers efficient?
> they use very little power when switched on when no load is applied
