P18: Motors, Generators and Transformers Flashcards
Describe the magnetic field patterns with like poles facing each other.
Bend away from the midpoint.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/189/138/219/a_image_thumb.jpg?1463388496)
Describe the magnetic field patterns with unlike poles facing each other.
The field between the poles is uniform.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/189/138/220/a_image_thumb.jpg?1463388497)
What is special about a uniform field?
The magnetic field lines are parallel to each other.
What metal is used for the core of electromagnets?
Iron (Easily magnetised and demagnetised)
Name for metals that can be magnetised/ demagnetised easily
ferrous metals
4 examples of electromagnets
> Scrapyard cranes > Circuit breakers > Electric bells > Relays
Increasing _____ makes the magnetic field of an electromagnet stronger.
Current
What surrounds an electromagnets core?
A coil of insulated wire
How can the size of the electromagnetic force be increased
Increasing the current Using a stronger magnet
In the motor effect, when is the force greatest?
When the wire is perpendicular to the magnetic field.
What are the magnetic field lines around a wire?
Circles centred on the wire in a plane perpendicular to the wire.
Reversing the direction of the current…
…reverses the magnetic field lines
The Motor Effect
When a CURRENT is passed along a wire in a magnetic field, A FORCE IS EXERTED on the wire by the magnetic field.
In the motor effect, when is the force zero?
When the wire is parallel to the magnetic field.
Fleming’s Left Hand Rule
Movement
Field (N to S)
Current
![](https://s3.amazonaws.com/brainscape-prod/system/cm/189/138/237/a_image_thumb.png?1463388500)
Commutator for DC
Split Ring- Reverse the current on every half turn to keep the motor spinning constantly.