Section 6 - Magnetism and Electromagnetism Flashcards
What do magnets do to other magnets? *
Like poles repel and opposite poles attract
Magnetic materials can induce magnetism within objects that are made of magnetic materials, but don’t show properties of magnetism
What are the properties of magnetically hard materials? *
They maintain their magnetic properties for a long period of time / permanently.
They are hard to demagnetise
What are the properties of magnetically soft materials? *
It loses its magnetic properties as soon as it leaves a magnetic field
What is a magnetic field line?
They are used to show the size and direction of magnetic fields. They always point form North to South
How is magnetism induced in some materials when they are placed in a magnetic field? *
The magnetic field encourages the electrons of the non-magnetic material to align and form poles.
This can happen in iron, cobalt and nickel
Describe experiments to investigate the magnetic field pattern for a permanent bar magnet and that between two bar magnets
You can use iron filings or multiple compasses to see the magnetic field lines coming out of a bar magnet or between two bar magnets
How do you produce a uniform magnetic field line?
If you put two permanent bar magnets together with their north and south touching, then they will form the same magnetic field as if they were one bar magnet.
What does an electric current in a conductor produce?
An electric current in a conductor produces a magnetic field around it. (Right Hand Rule)
Describe the construction of electromagnets *
Wrap a piece of wire around a soft magnetic material.
When there is a current in the wire, a magnetic field is induced in the object.
Sketch a magnetic field pattern for a straight wire when carrying a current *
a
Sketch a magnetic field pattern for a flat circular coil when carrying a current *
a
Sketch a magnetic field pattern for a solenoid when carrying a current *
a
What happens to a charged particle when it moves in a magnetic field? *
If a charged particle moves through a magnetic field, it will experience a force. Unless it is parallel to the direction of the magnetic field, in which case it won’t experience a force.
What happens when a current-carrying wire is put in a magnetic field?
A force is exerted
Fleming’s Left Hand Rule:
- Force is Thumb
- Field is Pointer Finger
- Current is Middle Finger
Describe how simple d.c. electric motors work
In a d.c. motor, there is a wire in a magnetic field.
The force it experiences turns it around.
This turns the split ring commutator, which is where charge goes form the brushes into the wires
Describe how a loud speaker works
A coil is in a magnetic field.
when a current rush through the wire, it will experience a force that pushes it away from the field.
this in turn pushes a cone which makes the sound.
Whatever frequency the AC current is at, the coil will move at that frequency, making a note of a certain pitch
How can you increase the force on a current-carrying conductor in a magnetic field?
You can increase the strength of the field
You can increase the current
How can you induce a voltage using a magnetic field? How can you change the voltage induced?
If you move a current-carrying wire back and forth across a magnetic field, a voltage will be induced
If you move a magnet back and forth through a coil of current-carrying wire, a voltage will be induced
If you increase the magnetic field strength, quicken the movement or increase the coils of wire, you can increase the voltage induced
How can you induce a current using a magnetic field?
How can you reverse the direction of the induced current?
What factors would affect the size of the induced current?
If you move a magnet through a coil of wires (solenoid) a current can be induced.
You can reverse the magnet or its direction of movement
Speed of the magnet going through the coil
Magnetic field strength of the magnet
Number of turns in the coil
Describe the structure of a transformer and how it performs its role? *
It will have a primary and secondary coil joined with an iron core.
When an alternating voltage is applied across the primary coil, the magnetically soft core magnetises and demagnetises quickly. This induces an alternating voltage in the secondary coil
What is a step-up and step-down transformer and what is it used? *
Step-Up Transformers step the voltage up. They have more turns on the secondary coil than the primary coil
Step-Down Transformers step the voltage down. They have more turns on the primary coil than the secondary coil
What is the relationship between input (primary) and output (secondary) voltages and the turns ratio for a transformer? *
Input (Primary) Voltage / Input (Secondary) Voltage is equal to Number of Turns on Primary / Number of Turns on Secondary
Describe the relationship between input power and output power *
Input Power = Output Power
