Magnetism And Electromagnetism Paper 2 Flashcards
What is Fleming’s left hand rule?
Thumb is force (motion)
Index finger is magnetic field
Middle finger is current
What happens when u put a moving wire with a complete circuit within a magnetic field?
It will induce a current that is alternating relative to the direction of the wire moving.
What happens when a moving wire with an incomplete circuit is put into a magnetic field?
It will induce potential difference that is alternating relative to the wire’s direction of movement.
What are 3 ways a generator can be altered to increase the potential difference?
Increase number of coils in wire
Increase speed of wire’s movement
Increase strength of magnetic field
What happens when current flows through a wire?
It produces a magnetic field
What is a solenoid?
A wire shaped into a coil
Name magnetic metals
Iron, cobalt, nickle
What is an induced magnet?
A material that becomes magnetic when placed into a magnetic field
What is the motor effect?
When a wire that is carrying a current produces a magnetic field with in turn causes a resultant force to exert force onto the wire
How are alternators used to produce an A.C current?
A coil of wire is placed into a magnetic field. This is connected to 2 slip rings, which allows current to pass through to an external circuit. Potential difference alternates due to the wire rotating, which in turn causes the current to alternate.
How does potential difference alternate in the wire?
When horizontal (parallel to the magnet), the potential difference is at its highest. However, when vertical (perpendicular to the magnet) the potential difference is at zero.
How do dynamos produce D.C current?
A rotating is placed into a magnetic field. A split ring is used to allow current to constantly flow in one direction.
How is the magnetic field’s strength around a wire affected?
Distance from wire
Magnitude of current
What can affect the strength of a solenoid?
NO. of coils
current in wire
Soleniod + iron core =?
Electromagnet
How can a solenoid be used in a door lock?
When the switch is pressed, current flows through the coil
The iron core becomes magnetised and attracts the iron bolt
The door can then be opened
How are electrical signals converted into sound waves in a speaker?
An alternating current is sent through the coil, which generates an electromagnetic field
The electromagnetic field and the permanent magnet interact, generating a force
The force makes the cone move
The alternating current constantly changes the direction of the force
This makes the cone vibrate forwards and backwards
The cone’s vibrations create variations in air pressure (sound waves)
As a result, sound is produced
What is the generator effect?
Moving a wire (conductor) at right angles to a magnetic field which induces p.d to produce a current
How do sound waves convert into electrical signals in a microphone?
sound waves hit the diaphragm of a microphone
The diaphragm is a thin membrane that vibrates with the same frequency and amplitude as the sound wave
The diaphragm passes the vibrations on to the coil
The coil moves within the magnetic field, which generates a current.
How do transformers work?
An alternating current flows into the primary coil
The primary coil is a solenoid and it induces a magnetic field
The iron core magnetises and demagnetises as the current changes
The changing magnetic field passes through the secondary coil and induces a potential difference in it
If the secondary coil is part of a complete circuit, an alternating current flows through the circuit
What are step up transformers?
Have more turns in secondary coil than primary and this increases potential difference
What are step down transformers?
They have more turns in primary coil than secondary and this decreases potential difference
