P4 Flashcards
Where is the force of magnetism strongest on a magnet?
The force of magnetism on a magnet is strongest at the north and south poles
Which are the three magnetic materials
Iron, cobalt and nickel are the three magnetic materials
Give the definition of a magnetic field
A magnetic field is the region around a magnet where another magnet/ magnetic material will experience a force
Which way do field line arrows point?
Field line arrows always point north to south
What happens when you place two permanent magnets with opposite poles next to each other
Two permanent magnets with opposite poles create a uniform field
What are magnetic field lines used for?
Magnetic field lines are used to show the size and direction of a magnetic field
What is the strength of a magnetic field called?
The strength of a magnetic field is called magnetic flux density and is measured in teslas (T)
Finish the sentence
Like poles…
Like poles repel
Finish the sentence
Opposite poles…
Opposite poles attract
Finish the sentence
Both poles attract…
Both poles attract non magnetic materials
What will happen to a magnetic material when brought near a permanent magnet?
The magnetic material will become an induced magnet. Most induced magnets will lose their magnetism when moved away
Give two ways we can see magnetic field lines in the lab
One way we can see magnetic field lines in the lab is through putting the magnet under a piece of paper and scarring iron filings over which will align themselves with the field lines
Am alternative way of seeing field lines in using a compass. Put a compass next to a magnet and Mark either end of the needles. Move it to the tip and Mark the tip again and repeat to form field lines
What is electromagnetism
Electromagnetism is the basis that when an electric current flows through a material and magnetic field is created around it
What are the magnetic fields around a straight current carrying wire made up of?
The magnetic fields around a straight current carrying wire are concentric circles
How can we find the direction of the magnetic field lines around a straight current carrying wire?
To find the direction of the field Lines around a straight current carrying wire we can use the right-hand rule
How can we prove that current creates a magnetic field
We can prove the current creates a magnetic field by using a compass which will point North when turned off but will deflect when turned on
What’s the magnetic fields around the flat circular current carrying coil made up of
The magnetic fields around a flat circular current carrying coils are made up of concentric elipses
What is a solenoid
A solenoid is a coil of wire acting as a magnet when carrying a current-it is an electromagnet.
How can we increase the magnetic effects of the north and south pole of a solenoid?
We can increase the magnetic effects of a solenoid north and South Pole by:
1) increasing the current
2) increasing the number of coils (but length stays the same)
3) decreasing length (but number of could stays the same)
4) decreasing cross sectional area
5) adding an iron core
What is the motor effect
The motor effect is when a current carrying wire is put at 90 degrees between two magnetic poles the wire will experience a force
How can you determine the direction of the force produced by the motor effect
To determine the direction of the force produced by the motor effect use Flemings left hand rule
1) put your first finger in the direction of the magnetic field
2) put your second finger in the direction of the current
3) your thumb will point in the direction of the force
How does an electric motor work?
A loop of current carrying wire is put between two magnetic poles using Fleming‘s left-hand rule one side of the wire experience as an upward force and one side experiences a downwards so the loop rotate 90°. The split ring commutator switch is the direction of the current when the loop hits 90° To keep the loop rotating.
How does a loudspeaker work?
1) A coil of wire is wrapped around the end of a cone
2) The coil is connected to an AC power supply
3) A permanent magnet is placed inside the coil
4) When turned on the current passing through the coil creates a magnetic field
5) The magnetic field interacts with the magnetic field of the magnet creating a force causing the cone to move
6) when the AC supply switches force moves in the opposite direction
7) The constant changing of the force causes the cone to vibrate creating sound waves
Definition of electromagnetic induction
electromagnetic induction is the production of voltage across the conductor due to a change in its external magnetic field
Explain using examples how the generator effect works
if we were to move a piece of wire through a magnetic field a potential difference will be induced along the ends of the wire we moved in the opposite direction the potential difference has reversed direction. If we were to move a complete circuit through a magnetic field we would induce current the direction of the current would also switch from the direction of movement switches
What is an alternator
alternator is a coil of wire/magnet rotating magnetic field to produce an alternating-current based on the generator affect
How does an alternate to produce an alternating-current ?
Alternator uses slip rings which don’t swap every half turn this means that the potential difference is reversed every turn producing and alternating-current .
What is the Dynamo ?
Dynamo is a coil of wire rotating in a magnetic field to produce a direct current based on the generator effects
How does a Dynamo produce a direct current ?
Dynamo produces a direct current three using a split ring commutator which swaps the connection every half turn to keep the current flowing one way.
Explain how the microphone works
The microphone consist of a magnet attached to a coil of wire which is attached to an alternating-current attached to a piece of plastic called the diaphragm. When soundwaves hit the diaphragm they cause it to vibrate this causes the wire to move in and out of the magnetic field this induces a potential difference across the ends of the wire and the potential difference is passed through an amplifier to loudspeaker.
What is a transformer ?
Transformer is an appliance that changes the size of the potential difference of an alternating-current
Explain what a step up transformer is
a step up transformer is appliance which increases the potential difference of alternating-current. And alternating-current is attached to a coil of wire wrapped around an iron core as a current flows through the primary coil it generates a changing magnetic field this magnetic field transmitted along the broken core and through to a secondary coil of wire which induces a potential difference of the secondary coil . The potential difference produced in the secondary coil is greater than a primary coil in a step up transformer because the number of turns in secondary coil is greater .
Explain what is stepdown transformer is
A step down transformer is an appliance that decreases the potential difference of an alternating-current. A primary coil wrapped around an iron core is attached to alternating-current as the current flows to the primary call it generate the change in magnetic field this magnetic field is transmitted along the iron core to a secondary coil which induces a potential difference . The potential difference induce second coil is less then at the primary coil as there is less number of turns.
Potential difference across primary coil /potential difference across secondary coil=
Number of turns in primary core/number of turns on secondary coil
