Electromagnetism Flashcards
What is electromagnetic induction?
The creation of a voltage (and maybe a current) in a wire which is experiencing a change in magnetic field
A coil in a moving…
…magnetic field produces a current
A moving current in a…
…coil produces a magnetic field
How can you make an electromagnet stronger? (3)
- Use more current
- More turns on the coil
- Use an iron core
How can you make the voltage larger?
- Use a stronger magnet
- Increase speed of magnet
- More turns on the coil
What is direct current?
Current that flows only in one direction
What is alternating current?
Current that flows in both directions continuously
What type of current do transformers use?
Alternating current
What is the magnetic field like inside a coil of wire?
Strong and uniform
Why is iron used in transformers?
It is a soft magnetic material - good because it needs to magnetise and demagnetise 50 times a second (50 Hz UK mains)
What will charged particles in a magnetic field feel, as long as they’re not moving parallel to field lines?
A force
What angle must a wire be at compared to the magnetic field to experience the full force?
90 degrees
What speeds up a DC electric motor? (4)
- More current
- More turns on the coil
- A stronger magnetic field
- A soft iron core in the coil
What does a split-ring commutator do in a DC electric motor?
It swaps the contacts every half turn to keep the motor rotating continuously in the same direction
How can the direction of a DC motor be reversed?
- Swap the polarity of the DC supply
* Swap the magnetic poles over
