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P7 Pre-Learning - Coggle Diagram
P7 Pre-Learning
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L2 - Electromagnets
- Conventional current - Positive to negative
- Actual current - Negative to positive
When current flows through a wire, a magnetic field is induced; the direction of this magnetic field can be predicted using the right hand rule.
If we place a compass next to a wire that does not have a current flowing through it; the north side of the needle will point towards the Earth's magnetic field; it will change when a current flows.
A larger current will produce a stronger magnetic field. The number of turns in a solenoid also increases the magnetic field strength.
If a piece of iron is placed within a solenoid magnet, this creates an electromagnet. These types of magnets can be turned on or off.
L10 - Transformers
A transformer consists of two separate coils wrapped around an iron core (this increases the magnetic field strength).
As an AC (a changing magnetic field is needed) flows through the primary coil and induces a magnetic field, this field is transferred to the secondary coil, inducing a potential difference.
The power in the primary coil is equal to the power in the secondary coil. (If the transformers are 100% efficient).
The power lost as heat in the national grid depends on the square of the current so current is reduced and PD is increased.
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L5 - Electric Motors
If we apply the motor effect to a loop of wire, we will have a moment established on the left hand and right hand side. When the loops has rotated 90 degrees, we must use a split ring commutator.
At 90 degrees, the split ring commutator loses contact with the wire and the circuit is broken (the circuit continues to rotate due to momentum).
L4 - The Motor Effect
When a wire that has a current flowing through it is placed perpendicularly to a magnetic field, it experienced a force; the direction of this force can be found using Fleming's left-hand rule.
L9 - Microphones
Microphones consist of a coil of wire with a permanent magnet within connected to a sheet of plastic known as a diaphragm. Sound waves cause the microphone to vibrate back and forth, moving the coil back and forth; generating a PD.