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Flashcards

Physics: Chapter 16: Magnets Part: 2

HRYN red GCSE Science English 57 cards

Label a D.C. Motor

Cards in this deck (57)

  1. 1What is the Left hand rule used for (Fleming's)? Does it have a power supply?Turning electricity to force
    The motor effect
    With a power supply
  2. 2What are all the fingers for Fleming's Left hand rule represent?Thumb - force/ direction of motion
    First finger - direction of magnetic field (North to South)
    Second finger - direction of current (positive to negative)
  3. 3What happens when a wire carrying an electrical current (which generates its own magnetic field) is placed into a magnet's magnetic field?The tow magnetic fields interact and the wire experiences a force.
  4. 4What happens to the wire when you reverse the current, reverse the field and reverse both?Current: Moves in the opposite direction. Reverse the field: moves in opposite direction
    Reverse both: moves in same direction
  5. 5The wire has to be 90 degrees parallel to each other. What happens if they are parallel?No force is felt if they are parallel - not cutting magnetic field.
  6. 6What can a charged particle moving be considered as?a current and will have a magnetic field
  7. 7What will happen if a charged particle is beamed into a magnetic field?like A CURRENT-CARRYING CONDUCTOR THE FIELDS INTERACT AND THE CHARGED PARTICLE WILL GET DEFLECTED. use Fleming's LEFT-HAND RULE TO WORK OUT DIRECTION OF THE FORCE. A NEGATIVE CHARGE, ELECTION HAS A BACKWARDS CURRENT AS CURRENT FORES FROM POSITIVE TO NEGATIVE. THE CHARGED PARTICLES ALREADY HAVE VELOCITY SO MOVE IN A CURVED PATH.
  8. 8What does a current-carrying coil in a magnetic field experience?A turning effect
  9. 9Label a D.C. MotorDont forget split ringsLabel a D.C. Motor
  10. 10What is the use of split rings?So that rotation continues in same direction
  11. 11How do you increase the turning effect of a D.C Motor?Increasing current
    Using a stronger mangnet
    Increase number of coils/area
  12. 12How can you reverse the rotation of a D.C Motor?Reversing the battery
    Reversing the poles
  13. 13What does a DC motor run on?A direct current
  14. 14How does a DC Motor work?When a current carrying coil is in a magnetic field, it experiences a turning effect, the coil if free to rotate and the commutator is fixed to the coil and rotates with it and the commutator (split rings) changes direction of the current through it, so the forces change direction and keep the coil turning. The brushes are 2 contacts which rub against the commutator and keep the coil connected to battery, usually made of carbon. The maximum turning effect with when the coil is horizontal. There is no force when the coil is vertical but it always overshoots this positions.
  15. 15What are the forces from the magnets? How is a turning force created?Opposite on opposite side of the coil and each causes a moment about the axis in the same direction resulting in a turning effect.
  16. 16What does e.m.f stand for?Electro-motive force (voltage)
  17. 17What happens when a conductor cuts magnetic field lines?An e.m.f(voltage) i induced (created) int eh conductor, causing current to flow if there is a complete circuit.
    Magnetic field lines must be cut by a conductor for emf to be induced.
  18. 18What are ways the induced EMF can be increased by?Moving the wire faster - more lines cut per second
    Using a stronger magnet - more field lines
    Increasing the length of wire in magnetic field ie looping wire through field several times. - more field lines cut
  19. 19What are 2 ways to induce em.f?Move a conductor in a magnetic field - relative movement
    Move a magnetic field around a conductor.
    Needs to be relative movement between conductor and magnetic field (not both moving)
  20. 20How can the current and EMF direction be reversed by?Moving the wire in the opposite direction
    Turning the magnet round so that the field direction is reversed
  21. 21What will the magnetic field in duced in the coil be to the changing cause?oppose ie the magnet's magnetic field. This means the North pole moving into the coil induces a North pole on the right of the coil which will repel the magnet.
  22. 22What will happen when the north pole of the magnet reaches halfway into the coil?The current will switch direction and the N-pole of the coil will be on the left.
  23. 23When is Fleming's Right Hand Rule used/ called?Generator effect
    No Power/cell
  24. 24What do the different fingers represent in Fleming's Right Hand Rule?Thumb - force
    First finger - magnetic field
    Second finger - current
  25. 25What is Current?Flow of charge
  26. 26What is the graph of a Direct Current and a Alternating CurrentDC - electrons flow around the circuit in one direction: straight line
    AC - Electrons oscillate (vibrate back and forth) curving positive and negative
  27. 27Periodtime for one cycle (revolution)
  28. 28What are the 3 things you need for electromagnetic induction?Magnet
    Conductor
    Movement
  29. 29What does the coil do in a A.C Generator?The coil is rotated in a magnetic field, this induces a current. As the coil moves it cuts the magnetic field lines of the permanent magnet- this induces an emf int eh coil - induced current flows
  30. 30What are the roles of Slip Rings?Connect the coil to a circuit, each slip ring is connected to a different end of the coil. They allow a continuous connection between stationary and moving parts, allowing the coil to turn freely without wires getting tangled.
  31. 31What are the ways to increase the induced emf in a A.C Generator?Turn the coil more rapidly
    Use coil with more turns/ use a coil with a bigger area
    Use stronger mangets
  32. 32What does a motor use What does a generator use to connect it to a circuit?Motor - split ring commutator
    Generator - slip rings
  33. 33How do you calculate Frequency?1/T
    T = time period
    Hz
  34. 34What is the peak on a coil position and voltage-time graphMaximum change of magnetic field lines
  35. 35How do you draw a coil position and voltage time graph with arrows?Can go up or down and then both left to right *
  36. 36What are step up and step down transformers?Change Voltage
  37. 37Why is electricity transmitted at high voltages in power lines?To reduce thermal energy/ power loses by heating due to resistance in cables
  38. 38What is the Equation for Power? Word and symbolPower = Current + Voltage
    P = IV
  39. 39How do you calculate Electrical energy?Voltage * Current * time
    E = VIt
    V * A * s
  40. 40What happens when voltage is increased?Current is decreased
  41. 41How is voltage increased?Using a step-up transformer
  42. 42What is the mains electricity in the UK?230V
  43. 43What do you use to change the potential difference (voltage) of an alternating current supply?Electromagnetic induction
  44. 44Give a diagram of a Transformer StructureGive a diagram of a Transformer Structure
  45. 45What does the primary coil act as in a Transformer? What does it do?Like an electromagnetic.
    When current flows and magnetizes the iron core with an alternating magnetic field.
  46. 46What does the iron core do?Concentrates the magnetic field, making the magnetic field stronger, challenging the field from the primary to secondary coil.
    Easily magnetizes and demagnetizes.
  47. 47What are the different Transformers? What do they do to the voltage? Does the secondary coil have more turns or less?Step Up - increases voltage. Secondary coil has more turns
    Step Down - decreases voltage
    Secondary coil has fewer turns
  48. 48What does more turns in a coil do?More magnetic field lines cut so larger emf
  49. 49DO Transformers work with AC or DC and why?AC - Don't work with direct current as no changing magnetic field n secondary coil so no emf is induced.
  50. 50What 3 things are involved in electromagnetic induction?Magnetic field
    Conductor
    Movement
  51. 51What does the AC provide?Provides alternating magnetic field which provides the movement.
  52. 52Give the Transformer OperationAlternating Current flowing through primary coil sets up alternating magnetic field in the iron core. Magnetic field cutting the secondary coil induces an emf causing current to flow if there is a circuit.
  53. 53What is the Turns Ratio Equation?Vp / Vs = Np/Ns
    Input AC voltage / output AC voltage = Turns on the primary coil / Turns on the secondary coil
  54. 54What happens if a transformer is 100% efficient?Power in = Power Out
  55. 55What is the equation for if a transformer is 100% efficient?IpVp = IsVs
    Currentp Voltagep = Current sVoltages
  56. 56What is the equation for if a transformer is 100% efficient?Ip/Is = Vs/Vp = Ns/Np
  57. 57What is the equation with transformers and voltage and current?Input Voltage * Input Current = Output Voltage * Output current

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GCSE Science (Physics) Flashcards on Physics: Chapter 16: Magnets Part: 2, created by HRYN red on 13/10/2020.
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HRYN red
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