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Question-1. What are the poles of a magnet?
Answer-1: The place where the magnetic forces are strongest.
Question-2. What happens when two magnets are brought close to each other?
Answer-2: They exert a force on each other.
Question-3. What happens when two like poles of magnets are brought close to each other?
Answer-3: They repel each other.
Question-4. What happens when two unlike poles of magnets are brought close to each other?
Answer-4: They attract each other.
Question-5. What type of force is magnetism an example of?
Answer-5: A non-contact force.
Question-6. What is a permanent magnet?
Answer-6: One which produces its own magnetic field.
Question-7. What is an induced magnet?
Answer-7: A material that becomes a magnet when it is placed in a magnetic field.
Question-8. What happens to an induced magnet when it is taken out of a magnetic field?
Answer-8: It loses most or all of its magnetism quickly.
Question-9. What is the only force that is caused by an induced magnet?
Answer-9: A force of attraction.
Question-10. What is a magnetic field?
Answer-10: The region around a magnet where a force acts on another magnet or on a magnetic material.
Question-11. What materials are magnetic?
Answer-11: Iron, cobalt, nickel, steel (an iron alloy).
Question-12. What type of force exists between a magnet and a magnetic material?
Answer-12: Attractive magnetic force.
Question-13. What does the strength of the magnetic field depend upon?
Answer-13: The distance it is from the magnet. The field is strongest at the poles.
Question-14. How do we define the direction of the magnetic field?
Answer-14: The direction of the magnetic field at any point is given by the direction of the force that would act on another north pole placed at that point.
Question-15. What direction do magnetic field lines point?
Answer-15: From the north seeking pole of a magnet to the south seeking pole of a magnet.
Question-16. How does a magnetic compass work?
Answer-16: It contains a small bar magnet that points in the direction of the Earth?s magnetic field.
Question-17. Why does Earth have a magnetic field?
Answer-17: It has an iron core.
Question-18. How can you use a compass to plot the magnetic field pattern of a magnet?
Answer-18: 1. Place the compass in the field around the magnet.
2. Draw a dot where the compass points (north and south)
3. Move the compass so that the south direction of the needle is at the dot you just drew
4. Repeat until the lines form a loop and connect the dots
Question-19. Describe how a dynamo works
Answer-19: 1. Generators rotate a coil in a magnetic field
2. As the coil rotates, a current is induced in the coil
3. The wire is attached to a split ring commutator
4. This keeps the current flowing in the same direction generating a direct current (DC)
Question-20. Describe how an alternator works
Answer-20: 1. Generators rotate a coil in a magnetic field
2. As the coil rotates, a current is induced in the coil
3. AC generators have slip rings and brushes so the current changes every half turn generating an alternating current (AC)
Question-21. Describe how loudspeakers and headphones works?
Answer-21: 1. A coil of wire is attached to a cone.
2. When an alternating current flows through the wire it creates a magnetic field.
3. The magnetic field interacts with the field from the permanent magnet
4. This produces a resultant force on the cone causing it to move
5. When the frequency of the AC current changes, the frequency of the sound changes
Question-22. Describe the magnetic field inside the solenoid?
Answer-22: It is strong and uniform (it has the same strength and direction at every point)
Question-23. Describe the shape of the magnetic field around a solenoid?
Answer-23: The same as the shape of a magnetic field around a bar magnet
Question-24. Describe what happens when a current carrying wire is put between magnetic poles?
Answer-24: The magnetic field around the wire interacts with the magnetic field it has been placed in, causing the wire and the magnet to exert a force on each other.
Question-25. How can the magnetic field of a solenoid be stopped
Answer-25: Turn of the current
Question-26. How can the size of the induced potential difference be changed
Answer-26: Increasing the speed of movement that the conductor is moving in and out of a magnetic field
Increasing the strength of the magnetic field
Turn the wire into a coil
Question-27. How can the strength of a solenoid be increased
Answer-27: By adding an iron core
Question-28. How do loudspeakers and headphones use the motor effect?
Answer-28: They convert variations in current in electrical circuits to the pressure variations in sound waves
Question-29. How do microphones use the generator effect
Answer-29: They convert the pressure variations in sound waves into variations in current in electrical circuits
Question-30. How does the magnetic field produced from an induced current interact with the magnetic field alread
Answer-30: The magnetic field created by a induced current acts against the change that made it
Question-31. How is the generator effect used in a dynamo
Answer-31: To generate a direct current (DC)
Question-32. How is the generator effect used in an alternator
Answer-32: To generate an alternating current (AC)
Question-33. To experience the full force from the motor effect, what direction does the wire have to be compared
Answer-33: 90o to the magnetic field.
Question-34. What does a basic transformer consist of
Answer-34: A primary coil of wire and a secondary coil of wire wound on an iron core
Question-35. What does Fleming?s left hand rule represent?
Answer-35: The relative orientation of the directions of the force, the current in the conductor and the magnetic field.
Question-36. What does the strength of a magnetic field depend on when a current flows through a wire?
Answer-36: The size of the current and the distance from the wire.
Question-37. What happens to a loop of wire carrying a current when placed in a magnetic field?
Answer-37: It rotates
Question-38. What happens to the magnetic field when a wire is shaped into a solenoid?
Answer-38: It becomes much stronger
Question-39. What happens when a current flows through a conducting wire?
Answer-39: A magnetic field is produced around the wire.
Question-40. What is a solenoid
Answer-40: A coil of wire
Question-41. What is a transformer
Answer-41: They can change the size of the potential difference
Question-42. What is an advantage of using an electromagnetic instead of a permanent magnet
Answer-42: The magnetic field can be turned on and off
Question-43. What is an electromagnet
Answer-43: A solenoid with an iron core
Question-44. What is produced in the iron core when an alternating current is applied in the primary coil of wire
Answer-44: A magnetic field that is changing
Question-45. What is the generator effect
Answer-45: The induction of a potential difference in a wire which is moving relative to a magnetic field
Question-46. What is the motor effect?
Answer-46: The term used when a current carrying wire experiences a force, causing it to move, when placed in a magnetic field
Question-47. What is the unit and unit symbol of current (I)?
Answer-47: Amps, A
Question-48. What is the unit and unit symbol of magnetic flux density (B)?
Answer-48: Tesla, T
Question-49. What is used in an electric motor to switch the direction of the current in the wires causing it to
Answer-49: A split ring commutator
Question-50. What symbol equation represents the force exerted on a conductor carrying a current at 90o
Answer-50: F = B I l
Question-51. What type of current does a transformer only work for
Answer-51: Alternating current
Question-52. What will affect the size of the force acting on the conductor in a magnetic field?
Answer-52: The magnetic flux density, the size of the current, the length of the conductor that?s in the magnetic field.
Question-53. What word equation represents the force exerted on a conductor carrying a current at 90o
Answer-53: Force = magnetic flux density x current x length
Question-54. When would a current be induced during the generator effect
Answer-54: If the conductor moving through the magnetic field was in a complete circuit
Question-55. When would a wire experience no force from the motor effect?
Answer-55: If the wire runs parallel to the magnetic field
Question-56. Why does a loop of wire rotate in a magnetic field?
Answer-56: The current travels in opposite directions through the magnetic field meaning the forces acting on the wire act in opposite directions
Question-57. Why is iron used as the core of a transformer
Answer-57: It is easily magnetised
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