Electromagnetic Flashcards
Define a permanent magnet
They produced thier own magnetic field
What are permanent magnets made of
Steel and impurities like aluminium
What is the magnetic field
A region where are the magnet magnetic materials experience a noncontact force
What are induced magnet
Magnetic material that turn into a magnet when put into a magnetic field
Permanent magnets always attract induced magnets
What happens when current flows through a wire
A magnetic field is created around the wire
What does changing the direction of current do
It changes the direction of the magnetic field
Describe the right hand thumb rule
Point Your thumb in the direction of current and call your fingers around this is the direction of the field
How can you increase the strength of the magnetic field of a wire
Play rappin’ the wire into a coil called a solenoids
Why do solenoids have a stronger magnetic field than a normal wire
Because the field lines line up with each other
Therefore ther are lots of field lines pointing in the same direction and that are very close together
What do the ends of a solenoid act like
The north and south pole of a bar magnet
How can u increase the field streangth of a solenoid
By putting an iron core which becomes an induced magnet
However if you stop the current the magnetic field disappears as it is an electromagnetic
What is the difference between a magnet and an electromagnet
You can turn electro on and off
What is the motor effect
When a current carrying wire is placed between magnetic poles , the magnetic fields of the poles and the wire interact which causes them to exert a force on each other .
How can the wire experience full force in the motor effect
The wire has to be at 90 degrees to the magnetic field as if it is parallel it will not experience any force
This is because force always acts at right angles to the magnetic field
What happens when current flows through the conductor
Force increases
What is the magnetic flux density
How many field lines are in a strength region which shows thev of the region
What does the force acting on a conductor in a magnetic field depend on
The magnetic flux density
The size of the current through conductor
And the length of the conductor in the magnetic feild
What equation is used when the current is at 90 degrees to the magnetic field
F= BIL
Force = magnet flux density x current x length
What is exerted on any current carrying conductor
Force
How can u find the direction of force on a current carrying conductor
Flemings left hand rule
Explain Flemings left hand rule
Using ur left hand point your first finger in the direction of the magnetic field
Second finger in the direction of current
Your thumb will show direction of force
How can you increase the force on a copper rod in experiment with a magnet and a circuit
Decrease the resistance of a variable resistor in the circuit
Use a stronger magnet
What is the name of the effect used by a moving coil loudspeaker to produce sound waves
Motor effect
Explain how a moving coil loudspeaker produces a sound wave
The current through the coil creates a magnetic field which interacts with the permanent magnetic field of a magnet
Therefore it produces a resultant force causing the coil to move producing sound waves
When direction of current reverses the direction of force will also reverse
A power supply has an alternator connected to a transformer transformer can be adjusted to have different numbers of terms on the coiled explain why
To vary the potential difference so you do not need a generator for each type of power supply device
In a simple DC motor how is an alternating current introduced in the coil
The coil move through the magnetic field of the polls on either side
So potential difference is induced across the coil
Therefore there is a complete circuit so current is also induced in the coil
Every half term the potential difference reverses direction so the current country reverse direction
Why are there slip rings on a DC motor
Stop wire from twisting together
The alternator from a portable power supply is disconnected from the transformer explain why the handle of the alternator becomes easier to turn
Because there’s no induced current so no magnetic field produced to oppose the movement of the coil
What is the function of a microphone
To convert soundwaves into variations in current
Quarter of a soil annoyed is to iron rods explain why they move apart when current is flowing through them
The roads become induced magnets with the same polarity therefore they repell
Why does the movement of a bar magnet induce a pd across a coil
As the magnetic failed around the coil changes
