Motor Effect Flashcards
What is an electromagnet?
● A solenoid with an added iron core
● Adding the iron core increases the
strength of the magnetic field
What is the motor effect?
When a force is exerted between a
magnetic field and a current-carrying
conductor placed in that field
What rule is used to determine the force
produced by the motor effect?
Fleming’s Left-Hand Rule
When using Fleming’s left hand rule what does the
forefinger represent?
The forefinger points in the direction of
the magnetic field
When using Fleming’s left hand rule
what does the middle finger represent?
The second finger points in the direction
of current flow in the conductor.
When using Fleming’s left hand rule what does the
thumb represent?
The thumb points in the direction of the
force produced by the motor effect.
What factors affect the size of the force on a
current-carrying wire in a magnetic field?
● The magnitude of the current flowing
through the conductor
● The strength of the magnetic field that
the conductor is placed in
If the direction of current in a current-carrying wire placed in a uniform magnetic field is reversed, what happens to the force?
The direction of the force is reversed
If the strength of the current in a current-carrying
wire placed in a uniform magnetic field is increased,
what happens to the force?
The strength of the force is increased
Give the equation linking force, magnetic flux
density, current and length
force (N) = magnetic flux density (T) x
current (A) x length (m)
F = BIL
What criteria must be met for the equation linking force, magnetic flux density, current and length to hold?
The conductor must be at right-angles to the magnetic field it is placed in
What is the unit used for magnetic flux density?
Tesla (T)
If the current and the magnetic field are parallel to
each other, which direction would the force act in?
No force will act
How does an electric motor work?
● A coil of wire, carrying a current, is placed in a magnetic field
● The forces on the two sides perpendicular to the field experience forces in opposite directions
● This causes a rotational effect
How are electric motors kept rotating?
A split ring commutator is used. This switches the current direction every half turn, which ensures that the coil keeps spinning
