Section 1 ELECTROMAGNETIC MACHINES
- Created by: Rebecca Pearson
- Created on: 19-05-13 19:32
View mindmap
- Section 1
- Magnetic Fields and Motors
- Wires carrying current in a magnetic field experience a force
- Current carrying wire and external magnetic fields interact
- Causes force on wire
- If current is parallel to flux lines no force acts
- Direction of force is perpendic. to current & mag field
- Direction of force given by LHR
- Wires carrying current in a magnetic field experience a force
- Current carrying wire and external magnetic fields interact
- Causes force on wire
- If current is parallel to flux lines no force acts
- Direction of force is perpendic. to current & mag field
- Direction of force given by LHR
- Direction of force given by LHR
- Current carrying wire and external magnetic fields interact
- Wires carrying current in a magnetic field experience a force
- Direction of force given by LHR
- Current carrying wire and external magnetic fields interact
- Magnetic field around current carrying wires
- Direction of mag field given by RHR
- Magnetic field is region where force is exerted on magnetic materials
- Represented by field lines
- Lines go from N to S
- Mag Field strength represented by how close lines are
- Size of force: F=BIl
- B is magnetic field strength
- Also called flux ddensity
- 1 tesla = Wb/m^2
- Size of force: F=BIl
- B is magnetic field strength
- Also called flux ddensity
- 1 tesla = Wb/m^2
- 1 tesla = Wb/m^2
- Vector quantity
- Also called flux ddensity
- B is magnetic field strength
- Size of force: F=BIl
- 1 tesla = Wb/m^2
- Vector quantity
- Also called flux ddensity
- B is magnetic field strength
- Forces on a loop can make a motor
- Wires carrying current in a magnetic field experience a force
- Electromag-netic induction
- Magnetic flux is total no. of field lines
- Mag field strength = mag flux density (B)
- Measures strength of mag field per unit area
- Mag flux = BA
- Flux linkage = mag flux x N (no. turns on coil)
- Faraday's Law
- Induced e.m.f is directly proportional to rate of change of flux linkage
- E.m.f is gradient
- Area under gives flux change
- Induced e.m.f is directly proportional to rate of change of flux linkage
- Changes in mag flux induce electromotive force
- E.m.f induced wherever there is relative motion between conductor and magnet
- Either conductor or mag field is still and other is moving
- E.m.f produced when flux lines are cut
- Only induces current if circuit is complete
- Charges accumulate on a conductor through mag field
- Conducting rod moving through mag field will experience force
- electrons accumulate at end of rod
- If rod is part of circuit then current will flow
- Called electromagnetic induction
- Induces e.m.f across end of rod (like battery)
- Conducting rod moving through mag field will experience force
- Lenz's Law
- Induced e.m.f is always in a direction that will oppose the change it causes
- Conservation of energy
- Find diction and current
- Induced e.m.f is always in a direction that will oppose the change it causes
- Magnetic flux is total no. of field lines
- Transformers and Alternators
- Transformers
- Work by electroma-gnetic induction
- Change the size of V for an AC
- Current flowing in primary coil produces mag flux
- Mag field passed through iron core to secondary coil
- Induces alternating voltage
- Step-up increase V by + turns on 2nd coil
- Affected by permeability and conductivity
- Permeance is amount of flux induced
- Higher the permeancethe greater the amount of flux flux induced
- Not 100% efficient
- Small losses of power in form of heat
- Heat produced by eddy currents in core
- Laminating core with insulation reduces
- Heat generated by resistancein coils
- Thick copper wire used to reduce resistance
- Heat produced by eddy currents in core
- Small losses of power in form of heat
- Part of national gird
- Electricity is sent round country at lowest current
- Low current means high voltage
- Step up transformers for transmission
- Step down for domestic use
- Step up transformers for transmission
- Work by electroma-gnetic induction
- Alternators
- Generator of A.C.
- Converts KE to electrical energy
- Induce current by rotating a coil in a mag field
- Transformers
- Magnetic Fields and Motors
Comments
Report