Magnetism (2) Flashcards
What is a permanent magnet
produce their own magnetic field constantly
What is an induced magnet
magnetic materials that become magnetic when placed within a permanent magnetic field
What is an electromagnet
an iron core wrapped in a current-carrying wire
When current flows, the iron becomes an induced magnet
How are magnetic fields drawn
Field lines go from north to south
closer together lines show a stronger magnetic field
the magnetic field is strongest at the poles
compasses show the direction of fields
what is the right thumb rule
pointing your right thumb in the direction of current through a wire, then observing the curvature of your fingers to determine the movement of the magnetic field around the wire
what is a solenoid
a coiled piece of wire around an iron core that increases the strength of a magnetic field
uses of electromagnets (2)
carrying metal objects
circuits
what is the motor effect
how is the strongest force achieved
how is the size of the force increased
The motor effect is the force experienced by a current-carrying wire in a magnetic field when the two interact
The force is strongest when the wire is at 90° to the magnetic field and zero when parallel.
The size of the force increases with stronger magnetic fields, higher current, or more wire in the field.
It causes the wire to move
what is Flemings left-hand rule
It shows the movement of a wire because of the motor effect
First finger- direction of magnetic field
seCond finger- direction of current
thuMb- shows the direction of the force (motion)
what are Motors and how do they work
electric motors use the motor effect to convert electrical energy into kinetic energy.
A current-carrying coil in a magnetic field experiences a force on both sides, making it spin.
Fleming’s Left-Hand Rule determines the direction of force on each side of the coil.
A split-ring commutator ensures the current direction reverses every half-turn, keeping the rotation continuous.
Increasing the current, magnetic field strength, or number of coils makes the motor spin faster.
Loudspeakers
loudspeakers use the motor effect to convert electrical signals into sound.
An alternating current (AC) flows through a coil of wire inside a magnetic field.
The current changes direction, causing the coil to experience a force that changes direction (Fleming’s Left-Hand Rule).
The coil is attached to a paper cone, which moves back and forth as the coil moves.
This movement creates variations in air pressure, creating sound waves.
Changing the frequency of the AC changes the pitch of the sound.
Increasing the current or magnetic field strength makes the sound louder.
The Generator effect
The generator effect is the process of generating an electrical current by moving a conductor through a magnetic field.
When a wire or magnet moves through a magnetic field, electrons in the wire are pushed, creating a current.
The size of the current depends on the speed of movement, the strength of the magnetic field, and the length of the wire.
The direction of the current can be reversed by changing the direction of movement or magnetic field (AC)
Fleming’s Right-Hand Rule is used to determine the direction of the induced current.
The generator effect is used in devices like electric generators and dynamos to produce electricity.
More coils and stronger magnets increase the current produced.
Microphones
Microphones use the generator effect to convert sound waves into electrical signals.
Sound waves cause a diaphragm to vibrate, which is attached to a coil of wire.
The coil moves within a magnetic field, inducing a current as it moves.
The varying sound waves cause the diaphragm and coil to move at different speeds, creating an alternating current that matches the sound.
The current’s strength and frequency correspond to the loudness and pitch of the sound.
What are Alternators
How can current be increased
Alternators use the generator effect to produce alternating current
A coil of wire rotates within a permanent magnetic field, causing the magnetism through the coil to change
This induces an AC in the coil by the use of a slip ring commutator
The current can be increased by increasing the speed of rotation, the strength of the magnetic field, or the number of coils.
Dynamos
How can the current be increased
Dynamos use the generator effect to produce direct current
A coil of wire rotates within a permanent magnetic field, causing the magnetism through the coil to change
This induces a direct current in the coil by the use of a split ring commutator
The current can be increased by increasing the speed of rotation, the strength of the magnetic field, or the number of coils.
What is an oscilloscope used for
they measure current and soundwaves and show how the potential difference generated in a coil changes over time
AC- a fluctuating line crossing the x-axis in the positive and negative directions
DC- Fluctuating line that stays above the x axis
the height of the line shows the generated potential difference
Transformers
(step up and down)
A transformer is an electrical device used to change the voltage of an alternating current
An alternating current in the primary coil creates a changing magnetic field in the iron core by it becoming rapidly magnetised and demagnetised, which induces an alternating current in the secondary coil. The size of the potential difference in the secondary core depends on the number of coils
Step-up transformer: Increases the voltage and decreases the current (more coils on secondary side)
Step-down transformer: Decreases the voltage and increases the current (more coils on primary side)
