Magnetic fields

• What is induced when current passes through a wire?

  A magnetic field
• How do the field lines of the induced magnetic field form around a wire?

  They form concentric rings
• What is the unit of magnetic flux density?

  Tesla
• How is one Tesla defined in terms of force, wire length, and current?

  1 N on 1 m of wire carrying 1 A
• What happens to the force on a current-carrying wire when it is parallel to a magnetic field?

  The force is 0 N
• What is the formula to find the magnitude of force on a wire in a magnetic field?

  F = BIl
• What does Fleming's left hand rule help determine?

  The direction of force on a wire
• What does the thumb in Fleming's left hand rule represent?

  The direction of motion/force
• What does the first finger in Fleming's left hand rule represent?

  The direction of the magnetic field
• What does the second finger in Fleming's left hand rule represent?

  The direction of conventional current
• How does a force act on charged particles in a magnetic field?

  It causes them to follow a circular path
• What is the formula for the force on a charged particle in a magnetic field?

  F = BQv
• What happens to the direction of the second finger in Fleming's left hand rule for negative charges?

  Reverse the direction of the second finger
• What does the force exerted on charged particles in a magnetic field act as?

  A centripetal force
• What is the formula to find the radius of a charged particle's circular path in a magnetic field?

  r = mv / BQ
• What is a cyclotron used for?

  Producing ion beams for radiotherapy
• What are the two semi-circular electrodes in a cyclotron called?

  Dees
• How does the magnetic field affect the speed of particles in a cyclotron?

  The speed does not increase due to the field
• What happens to particles when they reach the gap between the electrodes in a cyclotron?

  They are accelerated by the electric field
• What is magnetic flux?

  The magnetic field passing through an area
• How is magnetic flux calculated when the field is perpendicular to the area?

  Φ = BA
• What is magnetic flux linkage?

  Magnetic flux multiplied by the number of turns
• How can you find magnetic flux if the field is not perpendicular to a coil?

  Use trigonometry to resolve components
• What component of the magnetic field is required to calculate magnetic flux?

  The perpendicular component
• What is electromagnetic induction?

  Induction of emf when a conductor moves in a field
• What are the two laws governing electromagnetic induction?

  Faraday's law and Lenz's law
• What does Faraday's law state?

  Induced emf equals rate of change of flux linkage
• What does Lenz's law state?

  Induced current opposes the motion causing it
• How can you demonstrate Lenz's law with a falling magnet?

  Measure speed through a coil versus free fall
• What is the function of a transformer?

  Change the size of voltage with AC
• What are the main components of a transformer?

  Primary coil, secondary coil, iron core

  
• How does the primary coil interact with the secondary coil in a transformer?

  Induces a voltage in the secondary coil
• What is the equation relating the voltages and turns in a transformer?

  Ns/Np = Vs/Vp
• What is a step-up transformer?

  Increases voltage with more turns on secondary
• What is a step-down transformer?

  Decreases voltage with fewer turns on secondary
• How is transformer efficiency calculated?

  Power output divided by power input
• What is one main cause of energy loss in a transformer?

  Production of eddy currents
• How do eddy currents form in a transformer?

  Induced by the alternating magnetic field
• What is the relationship between the magnetic field and the direction of travel in charged particles?

  The force is always perpendicular to motion
• How do you take measurements from an oscilloscope?

  Count divisions and multiply by scale