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Questions and Answers
A copper wire is moved through a uniform magnetic field. Which action will not increase the induced electromotive force (e.m.f.) in the wire?
A copper wire is moved through a uniform magnetic field. Which action will not increase the induced electromotive force (e.m.f.) in the wire?
- Orienting the wire parallel to the magnetic field. (correct)
- Increasing the length of the wire within the magnetic field.
- Increasing the strength of the magnetic field.
- Moving the wire faster through the magnetic field.
A coil of wire is connected to a galvanometer. Which of the following scenarios would result in the largest induced current in the coil?
A coil of wire is connected to a galvanometer. Which of the following scenarios would result in the largest induced current in the coil?
- Holding a strong magnet stationary near the coil.
- Slowly moving a strong magnet away from the coil.
- Slowly moving a weak magnet toward the coil.
- Quickly moving a strong magnet toward the coil. (correct)
A square coil of wire is placed in a uniform magnetic field with its plane perpendicular to the field. If the coil is then rotated by 90 degrees so that its plane is parallel to the field in a short time interval, what factors determine the magnitude of induced e.m.f.?
A square coil of wire is placed in a uniform magnetic field with its plane perpendicular to the field. If the coil is then rotated by 90 degrees so that its plane is parallel to the field in a short time interval, what factors determine the magnitude of induced e.m.f.?
- Only the area of the coil and the strength of the magnetic field.
- Only the area of the coil and the number of turns in the coil.
- The area of the coil, the strength of the magnetic field, the number of turns in the coil, and the time interval of the rotation. (correct)
- Only the time interval of the rotation and the number of turns in the coil.
Two identical coils of wire are placed next to each other. Initially, there is no current flowing in either coil. If the current in coil A is suddenly increased, what effect will this have on coil B?
Two identical coils of wire are placed next to each other. Initially, there is no current flowing in either coil. If the current in coil A is suddenly increased, what effect will this have on coil B?
A magnet is rapidly pushed into a coil of wire. According to Lenz's Law, what effect will the induced emf have?
A magnet is rapidly pushed into a coil of wire. According to Lenz's Law, what effect will the induced emf have?
A copper wire is moved through a uniform magnetic field. Using the right-hand dynamo rule, if your index finger points in the direction of the magnetic field and your thumb in the direction of the wire's motion, what does your middle finger indicate?
A copper wire is moved through a uniform magnetic field. Using the right-hand dynamo rule, if your index finger points in the direction of the magnetic field and your thumb in the direction of the wire's motion, what does your middle finger indicate?
A bar magnet is held stationary near a coil of wire. Which of the following actions will NOT induce an emf in the coil?
A bar magnet is held stationary near a coil of wire. Which of the following actions will NOT induce an emf in the coil?
A north pole of a magnet is rapidly withdrawn from a coil of wire. According to Lenz's law, what polarity will be induced on the end of the coil closest to the departing magnet, and why?
A north pole of a magnet is rapidly withdrawn from a coil of wire. According to Lenz's law, what polarity will be induced on the end of the coil closest to the departing magnet, and why?
What is the fundamental principle underlying Lenz's Law?
What is the fundamental principle underlying Lenz's Law?
A rectangular coil is placed in a uniform magnetic field. Which action will induce the largest emf in the coil?
A rectangular coil is placed in a uniform magnetic field. Which action will induce the largest emf in the coil?
If a coil is moved parallel to a magnetic field, what is the induced EMF?
If a coil is moved parallel to a magnetic field, what is the induced EMF?
Which of the following is a correct statement about current flow?
Which of the following is a correct statement about current flow?
Flashcards
Electromagnetic Induction
Electromagnetic Induction
The generation of voltage due to the motion of a conductor through a magnetic field or a changing magnetic field around a conductor.
Induced Electromotive Force (EMF)
Induced Electromotive Force (EMF)
Voltage created due to electromagnetic induction.
When is EMF induced?
When is EMF induced?
An electromotive force is generated.
Magnet Stationary
Magnet Stationary
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Voltmeter
Voltmeter
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Induced EMF
Induced EMF
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Motion & EMF
Motion & EMF
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Lenz's Law
Lenz's Law
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Magnet In
Magnet In
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Magnet Out
Magnet Out
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Right-Hand Dynamo Rule
Right-Hand Dynamo Rule
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Current Direction
Current Direction
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Direction of Induced EMF
Direction of Induced EMF
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Study Notes
- Electromotive force (e.m.f.) is induced in a conductor when there is relative movement between the conductor and a magnetic field
Induction of Electromotive Force
- An e.m.f. is induced when an electrical conductor moves in a magnetic field.
- When a magnet moves through a conductor, field lines cut through the conductor's turns, inducing an e.m.f. in the coil.
- A changing magnetic field induces a current in a wire coil when a magnet is moved toward the wire
- A sensitive voltmeter measures the size of the induced e.m.f.
- A current is induced in the conductor if the conductor is part of a complete circuit.
- The voltmeter needle deflects when a magnet is pushed into the coil.
- There is no relative movement between the coil and the magnetic field when both the magnet and coil are stationary
- No magnetic field lines are being cut when there is no relative movement; therefore, no e.m.f. is induced
Lenz's Law
- Any magnetic field created by an induced emf will act to try to stop the wire or magnet from moving
- Lenz's law is demonstrated when a magnet is pushed into, or out of, a coil of wire
Magnet Pushed into a Coil
- The end of the coil closest to the magnet becomes a north pole if the magnet is pushed north end first into the coil
- The magnetic field due to the current opposes the magnet being pushed into the coil, therefore, the end of the coil closest to the magnet acts as a north pole and repels the north pole of the magnet
Magnet Pulled Away from a Coil
- The end of the coil closest to the magnet becomes a south pole if a magnet is pulled away from the coil of wire
- The magnetic field due to the current opposes the magnet being pulled away from the coil, therefore, it attracts the north pole of the magnet
Right-Hand Dynamo Rule
- The direction of induced emf can be determined using the right-hand dynamo rule when moving a wire through a magnetic field
Applying the Rule
- Point the first finger in the direction of the field
- The second finger points in the direction of the current/emf
- Current flows from the positive to the negative terminal of the battery, and current is always in the direction of positive charge carriers.
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