P4 Magnets Flashcards
What is the motor effect?
What is the formula?
The motor effect is when two magnets exert forces upon each other when their fields come in contact.
Force on wire is equal to its current, its length in the magnetic field, flux density of the magnetic field it is in.
F (Force) = B (Flux Density) * I (Current) * L (Length)
What is Fleming’s left hand rule?
Index = Field Direction
Middle = Current Direction
Thumb = Force Direction
Used to calculate the direction of force on a wire in a magnetic field
What is involved with an electric motor? Energy?
Electric Motor uses the motor effect to make electrical energy to kinetic energy.
Electric Motor consists of a length of wire with a current shaped as a coil in a magnetic field with a split-ring commutator to switch current direction.
How does an electric motor work?
A direct current flows in a loop of 2 side arms perpendicular to the field to experience a force. The 2 arms work in opposite directions so it rotates. The wire becomes vertical but is stuck because the forces cancel out. The split-ring commutator switches the direction and rotates the direction so the forces switch direction and continues to rotate.
What is a magnet and magnetic field?
Magnets are materials which experience a force in a magnetic field. A magnetic field is the region in which other magnetic materials experience a force.
What is an induced magnet and domain theory?
An induced magnet only exhibits magnetic properties when in a magnetic field. However, it does not exhibit magnetic properties when on its own. A magnet is made up of many small magnetic regions called domains that all line up. In induced magnets, they are not naturally lined up but when in a magnetic field, they do and so show magnetic properties.
How does solenoid enhance magnetic effect?
Many parallel loops make a coil, or solenoid. Each loop creates a field and adding them together produces a much stronger field that that of a single wire. By putting a material inside like an iron core, it creates a strong permanent magnet.
What are hard and soft magnets?
Hard magnetic materials continue to be lined up when you remove the magnetic field. Soft magnetic materials have their domains return to their original direction.
What does the magnetic field strength around a solenoid depend on?
-The magnitude of current
-The core of the solenoid (iron core)
-The number of coils
Measured in Teslas
What happens when you combine magnetic fields? Both ways?
You can combine the field in a wire with the field from a permanent magnet. This exerts a force on the wire. When two fields are in the same direction, they add up, if they are opposite, they cancel out.
Fingers of Fleming’s left-hand rule
Thumb = Force
Index = Field (North to South)
Middle = Current (positive to negative)
How do you calculate the size of force from 2 magnetic fields?
F = F * I * B
Magnetic Flux Density * Current * Length
What is electromagnetic induction?
You can produce an induced potential difference across ends of a wire if the wire is in a changing magnetic field so it cuts the field lines. This can happen when you move a conductor in a magnetic field.
What factors affects the induced potential difference?
Moving the wire faster, using a strong magnetic field, using more wire (loops/coils)
How do you know the direction of an induced potential difference?
When current flows in a conductor it produces a magnetic field and in a magnetic field, flux lines interact creating a new magnetic field. The magnetic field produced by the wire is in the opposite direction to the magnetic field created by the two interacting magnetic fields.
