Electric magnets Flashcards
(23 cards)
Name two sources of magnetic field
permanent magnet, electric current
Name 2 uses of electromagnet
Electric door lock and engines
What does strength of electromagnet depend on?
The number of turns of wire wound around the coil, and. The amount of current flowing through the wire.
What are the units of measurement for magnetic induction (magnetic field strength)?
B=1T(tesla)
Name two ways to demagnetize a permanent magnet.
High temperature and motion
Explain why cutting a permanent magnet in half results in two smaller magnets both of which have magnetic north and
south poles.
When you cut a magnet, the magnetic domains rearrange themselves, creating two smaller magnets
What is an electric motor?
Machine that convert electrical energy to mechanical energy
Name two devices in which electric motors are used.
Electric motors are used in water pumps, electric fans, electric mixers and washing machines.
Name main parts of an electric motor.
Stator, rotor
Explain how an electric motor works.
Most electric motors operate through the interaction between the motor’s magnetic field and electric current in a wire winding to generate force in the form of torque applied on the motor’s shaft.
Suggest two ways to increase the rotation speed of an electric motor.
Number of coils, incrase current
What is electromagnetic induction?
Electromagnetic induction - is a process in which electric current occurs in a conductor which is placed in a varying magnetic field or the conductor is moved in stationary magnetic field.
What is induced current?
The current produced by electromagnetic induction
What does the magnitude of induced EMF depend on?
Two Factors are
1. The change in magnetic flux;
2. Numbers of coils
What does the direction of induced EMF depend on?
DIRECTION of induced e.m.f depends on magnetic field direction and direction of conductor movement
Name two devices in which electromagnetic induction is used.
Two devices that use electromagnetic induction are electric generators and transformers.
What is a generator?
a device that converts mechanic energy to electric energy
Name the main parts of a generator.
Rotor and stator
Name one similarity and one difference between an electric motor and a generator.
Similliar: both have stator and rotor
Difference: el. generator converts mechanical to electric
generator converts electric to mechanical
What is a transformer?
a device that changes the voltage and strength of an AC circuit.
Name the main parts of a transformer.
The transformer consists of two coils placed on an iron core.
Why are transformers used in electric energy transmission lines?
to increase the voltage, decrease the current, and thus reduce energy losses
Explain how a transformer works.
The operation of the transformer is based on the phenomenon of electromagnetic induction.
The electric current flowing from the source in the primary winding creates a magnetic flux in the transformer core.
The magnetic flux induces an electrical voltage in the secondary winding.
