Electromagnetic Induction Flashcards
What is the generator effect?
When a wire is moved through a magnetic field, a potential difference is induced across the ends of the wire, when the wire is moved the other way through the wire, the potential difference changes direction. If there is a complete circuit then a current is induced, the current also changes direction when the direction of movement switches
How can the direction of an induced current?
Changing the direction of motion of the wire or changing the direction of the magnetic field
How can you increase the size of an induced current?
- By moving the wire faster
- Using stronger magnets
- Using more coils of wire so there is more wire moving through the magnetic field
How does an alternator work?
The two sides of the coil are attached to two different rings meaning an alternating potential difference and an alternating current is produced
If the rotation speed of the coil in an alternator is increased, what happens to the alternating current?
Its size and frequency increases
How does a dynamo work?
Both sides of the coil are connected to the same ring so when the coil rotates, the potential difference and current are not reversed, this causes a direct current to be produced
How does a loudspeaker work?
A cone has a coil of wire wrapped around one end of it, the coil of wire is connected to an AC supply, there’s also a permanent magnet that goes inside the coil of wire. As a current passes through the coil a magnetic field is generated, the magnetic field from the coil interacts with the magnetic field from the permanent magnet, these magnetic field either attract or repel each other causing a resultant force which causes the cone to move, when the current switches direction it causes the direction of the force on the cone to also be reversed, this causes the cone to move in and out causing sound waves to be generated
How does a microphone work?
A coil of wire is attached to a thin sheet of plastic called a diaphragm, the end of the coil of wire sits over a diaphragm, when soundwaves hit the diaphragm, they cause it to vibrate which causes the coil of wire to move in and out of the magnetic field, this induces a potential difference across the ends of the wire. The coil moving in and out of the magnetic field causes the potential difference to change direction, the switching potential difference is then passed through an amplifier and into a loudspeaker which massively increases the volume of the sound
In transformers what is the power of the primary coil equal to?
The power of the secondary coil
If the voltage of the primary of the primary coil is 10V and it has 5 coils, what is the voltage of the secondary coil with 10 coils?
20V
Why are step up transformers used in the national grid?
To increase voltage and decrease current, this means that energy loss as heat is reduced in the wires and also means thinner wires can be used which reduces cost
Why are step down transformers also used in the national grid?
To decrease the voltage of the electrical energy before it reaches homes and industrial buildings for safer use, reducing the voltage means there will be an increase in current
What does decreasing voltage do to current?
Increases it, this happens in step down transformers
What does increasing voltage do to current?
Decreases it, this happens in step up transformers
