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Questions and Answers
What are the three materials that can be made into temporary magnets?
What are the three materials that can be made into temporary magnets?
Which of these options are correct? (Select all that apply)
Which of these options are correct? (Select all that apply)
Magnetic field lines point from the South to the North pole of a magnet.
Magnetic field lines point from the South to the North pole of a magnet.
False
The Earth's magnetic core is above Canada and is a South Pole.
The Earth's magnetic core is above Canada and is a South Pole.
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The direction of current in a wire is dictated by the right hand grip rule.
The direction of current in a wire is dictated by the right hand grip rule.
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A solenoid has the same shape magnetic field as a bar magnet.
A solenoid has the same shape magnetic field as a bar magnet.
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What is the term for the movement of a wire in a magnetic field?
What is the term for the movement of a wire in a magnetic field?
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What is the name of the rule used to determine the force on a wire in a magnetic field?
What is the name of the rule used to determine the force on a wire in a magnetic field?
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A DC current creates a constant magnetic field.
A DC current creates a constant magnetic field.
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An alternator produces a DC current.
An alternator produces a DC current.
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The electric current in a dynamic microphone is proportional to the sound signal.
The electric current in a dynamic microphone is proportional to the sound signal.
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A _________ is a device that transforms the energy carried by an alternating current into a magnetic field and back again.
A _________ is a device that transforms the energy carried by an alternating current into a magnetic field and back again.
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A step-up transformer increases the voltage of the secondary coil, but decreases the current.
A step-up transformer increases the voltage of the secondary coil, but decreases the current.
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What type of current is produced by a dynamo?
What type of current is produced by a dynamo?
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What part of the dynamic microphone is free to move?
What part of the dynamic microphone is free to move?
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Study Notes
Magnetism and Electromagnetism
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Magnets:
- North and South poles; like poles repel, unlike poles attract.
- Permanent magnets always have poles.
- Induced magnets can be temporarily magnetized by stroking with a permanent magnet. This aligns magnetic domains.
- Iron, nickel, and cobalt are magnetic materials.
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Magnetic Fields:
- Field lines point from North to South.
- Strength decreases with distance from the magnet.
- Plotting compasses show the direction of the magnetic field.
- Earth's core creates a magnetic field; compass aligns with Earth's field lines, not Geographic North.
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Current and Magnetic Fields:
- Current produces a magnetic field around a wire (circular in shape).
- Right-hand grip rule determines field direction.
- Greater current, stronger field.
- Greater distance from wire, weaker field.
Solenoid
- The magnetic field shape is similar to a bar magnet.
- Coiling the wire enhances the effect.
- Using an iron core strengthens the magnetic field.
- Factors affecting solenoid strength include current, length, cross-sectional area, number of turns and using a soft iron core.
The Motor Effect
- Two magnets or a magnet and a current-carrying wire interact.
- Forces exist due to magnetic fields interacting.
- The force is at right angles to both the current and the magnetic field.
- Fleming's left-hand rule helps determine the direction of the force.
How Electric Motors Work
- A coil of wire rotates between permanent magnets (due to force changes)
- This is due to current flowing through a wire in a magnetic field.
- The wire experience a torque.
- This creates an alternating current (AC).
Electromagnetic Induction
- Relative movement between a conductor and magnetic field induces a potential difference.
- Changing magnetic field also induces potential difference. This creates a current if the conductor forms a complete circuit.
- The current created opposes the inducing change.
How Electric Generators (Dynamos) Work
- Similar setup to a motor; coil of wire rotates between magnets.
- Rotating the coil cuts through magnetic field, inducing a potential difference.
- A complete circuit produces current.
- Direct Current (DC) created using a split ring commutator; this ensures current is always flowing in the same direction.
Transformers
- AC in the primary coil creates a changing magnetic field.
- This induces a current in the secondary coil.
- More coils on the secondary coil means an increased voltage (step-up transformer).
- Fewer coils on the secondary coil means a decreased voltage (step-down transformer).
How Microphones Work
- Dynamic microphones use a coil of wire in a magnetic field to produce a current proportional to the sound signal.
- Sound pressure waves move the coil, creating the current.
Loudspeakers
- These work in reverse of a microphone.
- The current in the coil interacts with the magnetic field to move the cone of the loudspeaker.
- This produces sound pressure waves.
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Description
This quiz covers the fundamental concepts of magnetism and electromagnetism, including the properties of magnets, magnetic fields, and the relationship between current and magnetic fields. Students will explore key principles such as pole interaction, magnetic field strength, and applications of the solenoid. Test your understanding of these essential physics concepts!
