Using Magnetic Fields to Keep Things Moving
- Created by: BThorogood
- Created on: 18-03-14 19:28
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- Using Magnetic Fields to Keep Things Moving
- Electromagnets
- The forces between two magnets: like poles repel; unlike poles attract.
- A magnetic field line is the line, along which a plotting compass points.
- An electromagnet consists of a coil of insulated wire, wrapped round an iron core.
- Electromagnets are used in scrapyard cranes, circuit breakers, electric bells, and relays.
- The Motor Effect
- In the motor effect, the force:
- is increased if the current of the strength of the magnetic field is increased.
- is at right angles to the direction of the magnetic field, and to the wire.
- is reversed if the direction of the current or the magnetic field is reversed.
- An electric motor has a coil, which turns when a current is passed through it.
- In the motor effect, the force:
- Electromagnetic Induction
- When an electromagnet is used, it needs to be switched on or off to induce a pd.
- Electromagnetic induction is the process of creating a pd, using a magnetic field.
- When a conductor cuts the lines of a magnetic field, a pd is induced across the ends of the conductor.
- Transformers
- A transformer has an iron core, unless it is a switch mode transformer, which has a ferrite core.
- A transformer only works on AC because a changing magnetic field is necessary to induce AC in the secondary coil.
- A switch mode transformer is lighter and smaller than an ordinary transformer.It operates at high frequency.
- Transformers in Action
- Transformers are used to step pd up or down.
- For a step-down transformer, n(s) is less than n(p). For a step-up transformer, n(s) is greater than n(p).
- The transformer equation is: V(p)/V(s) = n(p)/n(s)
- V(p) is the primary pd
- V(s) is the secondary pd
- n(p) is the number of primary turns
- n(s) is the number of secondary turns
- For a 100% efficient transformer, V(p) x I(p) = V(s) x I(s)
- I(p) is the current in the primary coil
- I(s) is the current in the secondary coil
- A Physics Case Study
- We measures blood pressure, ECG potential differences, and exposure to ionising radiation in hospitals.
- We use physics in hospitals whenever:
- blood pressure (or temperature) is measured.
- an ECG recording is made.
- an endoscope is used.
- a scanner is used.
- Untitled
- Electromagnets
- Transformers
- A transformer has an iron core, unless it is a switch mode transformer, which has a ferrite core.
- A transformer only works on AC because a changing magnetic field is necessary to induce AC in the secondary coil.
- A switch mode transformer is lighter and smaller than an ordinary transformer.It operates at high frequency.
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