Mag Fields

• Field Strength is proportional to...


  speed of charge
• What do field lines represent?

  the magnetic flux
• Magnetic Flux Density

  force per unit current length
• define Tesla


  one newton per amp meter
• Tesla in terms of magnetic flux density

  one weber per meter squared 1Wb/m^2
• what force do all magnets produce?

  electromagnetic force
• A moving charge has what fields?

  Magnetic AND electric
• what is the flux density in uniform magnetic fields


  constant
• what is formed when an electrical current flows through a wire that is in a magnetic field?


  magnetic field around the wire
• How does the force in F = Bev effect a charged particle?


  makes charged particle deflect to oppositely charged pole
• Where does F = Bev work?


  when magnetic field is acting at right angles to the velocity of a particle
• what affects the velocity of a charged particle in a magnetic field?


  • mass of particle
  • radius of deflection
  • magnetic flux density
  • charge of the particle
• what can flux linkage be altered by?


  • magnetic flux density
  • area of coil
  • number of coils
  • angle between flux and area
• Faraday's Law


  the induced emf is directly proportional to the rate of change in flux linkage for a conductor
• what is the gradient in a flux linkage against time graph?


  emf
• Lenz's Law

  The induced emf will always be produced in opposite direction to change in flux linkage which causes it
• peak voltage


  maximum voltage from equilibrium
• peak to peak voltage


  maximum negative voltage to maximum positive voltage
• root mean square voltage


  initial voltage / root 2
• If a coil is made to rotate faster, how does this affect the pattern on an oscilloscope?

  Time period decreases and peak voltage increases
• If a coil is placed in a stronger magnetic field, how does this affect the pattern on an oscilloscope?


  peak voltage increases but time period does not change
• What path does an electron follow when it is moving at right angles to a uniform magnetic field


  circular
• State two situations in which a charged particle will experience no magnetic force when placed in a magnetic field


  when the particle is stationary and when the particle is moving parallel to field lines
• Principles of electromagnetism

  when electrical current flows in a wire, a magnetic field is formed around the wire
• how does the current affect electromagnetism?

  stronger current leads to stronger field, where change in direction of the current changes polarisation of magnetic field, no current = no field
• Does a stationary charged particle produce a field?

  no
• In F=Bqv how does the magnetic force act?

  as centripetal force
• When does F=Bqv work?

  when magnetic field is at right angles to velocity of particles
• In a transformer why is the core made of soft iron?

  so it can change it's magnetic field easily
• How to increase efficiency of transformer?

  insulated wires and laminated core
• why laminate the core?

  to prevent eddy current in the core
• What are eddy currents not good in transformers?

  magnetic field produced by eddy currents are in opposite direction the desired magnetic field direction
• Considering a positive charge, what do field lines show?


  path it will take
• Where is magnetic flux density said to be constant?

  in a uniform field
• What happens to a magnetic field if the direction of the current changes?

  magnetic field changes polarisation
• When does F =Bqv work?

  when magnetic field is acting at right angles to velocity of the particle
• Explain how the mass of a particle, affects the velocity of a charged particle in a mag field

  The mass is directly proportional to the radius of the path taken by the charge. So the greater the mass the greater the force required to maintain it’s circular motion
• Explain how magnetic flux density affects the velocity of a charged particle in a magnetic field

  The force experienced by the charged particle is directly proportional to the magnetic flux density. As the magnetic flux density increases, the force experienced by the particle also increases.
• Considering a wire carrying a current through a magnetic field, when is the emf induced largest?

  when the wire is parallel to the field
• Why is the emf induced largest when current is parallel to field lines?

  the magnetic flux through the wire changes at its fastest rate, resulting in the largest induced emf