Electromagnets Flashcards
in terms of magnetism what occurs when a current flows through a wire and the properties of the occurrence
it creates a circular magnetic field around the wire. The magnetic field can deflect the needle of a magnetic compass
How is the magnetic field generated by current’s strength increased
move it closer to the wire
if the current is increased
solenoid
A solenoid consists of a wire coiled up into a spiral shape.
The motor effect
A wire carrying a current creates a magnetic field. This can interact with another magnetic field, causing a force that pushes the wire at right angles.
Calculating the motor force force = magnetic flux density × current × length
READ IT AND UNDERSTAND
force = magnetic flux density × current × length
F is force in newtons (N)
B is magnetic flux density (magnetic field strength) in
tesla (T)
I is current in amperes - also
referred to as amps (A)
is length in metres (m)
force = magnetic flux density × current × length
when does the force on a given length of wire in a magnetic field increase
the current in the wire increases
the strength of the magnetic field increases
what is the motor effect when current and magnetic field are parallel with each other
non existant
How can an electric motor be created
A coil of wire carrying a current in a magnetic field experiences a force that tends to make it rotate. This effect can be used to make an electric motor.
What two features of a DC motor allow the coil to continue rotating even though it moves parallel to the magnetic field
the momentum of the motor carries it on round a little
a split ring commutator changes the current direction every half turn
What happens once the conducting brushes reconnect with the commutator after a half turn
current flows in the opposite direction through the wire in the coil
each side of the coil is now near the opposite magnetic pole
How does alternating current supplied to a loudspeaker create sound waves through a speaker
- a current in the coil creates an electromagnetic field
- the electromagnetic field interacts with the permanent magnet generating a force, which pushes the cone outwards
- the current is made to flow in the opposite direction
- the direction of the electromagnetic field reverses
- the force on the cone now pulls it back in
- repeatedly alternating the current direction makes the cone vibrate in and out
- the cone vibrations cause pressure variations in the air, which are sound waves
