Forces in Everyday Devices - Middle School Physical Science
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What is the name of the force that pushes or pulls on a current-carrying wire in a magnetic field?
What is the name of the force that pushes or pulls on a current-carrying wire in a magnetic field?
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Magnetic force on a current (motor effect). Current in a magnetic field experiences a force.
Magnetic force on a current (motor effect). Current in a magnetic field experiences a force.
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Which change increases induced current in a coil: moving the magnet faster or slower?
Which change increases induced current in a coil: moving the magnet faster or slower?
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Moving the magnet faster. Faster change in magnetic flux induces more current.
Moving the magnet faster. Faster change in magnetic flux induces more current.
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Which core material usually makes an electromagnet stronger: iron core or plastic core?
Which core material usually makes an electromagnet stronger: iron core or plastic core?
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Iron core. Iron concentrates and amplifies the magnetic field.
Iron core. Iron concentrates and amplifies the magnetic field.
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What happens to an electromagnet’s strength when more turns of wire are added to the coil?
What happens to an electromagnet’s strength when more turns of wire are added to the coil?
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It increases (more turns produce a stronger field). Each loop adds to the total magnetic field.
It increases (more turns produce a stronger field). Each loop adds to the total magnetic field.
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What happens to an electromagnet’s magnetic field strength when the current increases?
What happens to an electromagnet’s magnetic field strength when the current increases?
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It increases (stronger magnetic field). More current means more magnetic field strength.
It increases (stronger magnetic field). More current means more magnetic field strength.
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What is the name for a coil of wire that creates a magnetic field when current flows?
What is the name for a coil of wire that creates a magnetic field when current flows?
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Electromagnet (a current-carrying coil that acts like a magnet). Current through wire creates a magnetic field around it.
Electromagnet (a current-carrying coil that acts like a magnet). Current through wire creates a magnetic field around it.
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What is the name of the device that steps voltage up or down using induction between coils?
What is the name of the device that steps voltage up or down using induction between coils?
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Transformer. Uses changing magnetic field to induce different voltage in second coil.
Transformer. Uses changing magnetic field to induce different voltage in second coil.
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Which option best describes what a loudspeaker does using electromagnets?
Which option best describes what a loudspeaker does using electromagnets?
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Current changes create motion of a coil/cone to produce sound. Varying current creates varying magnetic force to vibrate speaker cone.
Current changes create motion of a coil/cone to produce sound. Varying current creates varying magnetic force to vibrate speaker cone.
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Which statement is correct: like magnetic poles attract or like magnetic poles repel?
Which statement is correct: like magnetic poles attract or like magnetic poles repel?
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Like poles repel; unlike poles attract. Same poles push apart; opposite poles pull together.
Like poles repel; unlike poles attract. Same poles push apart; opposite poles pull together.
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What is the term for producing current by moving a conductor through a magnetic field?
What is the term for producing current by moving a conductor through a magnetic field?
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Electromagnetic induction. Changing magnetic flux through a conductor induces current.
Electromagnetic induction. Changing magnetic flux through a conductor induces current.
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Which device converts mechanical motion into electrical energy using magnets and coils?
Which device converts mechanical motion into electrical energy using magnets and coils?
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Electric generator. Spinning magnets near coils induces current flow.
Electric generator. Spinning magnets near coils induces current flow.
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Which device converts electrical energy into mechanical motion using magnets and current?
Which device converts electrical energy into mechanical motion using magnets and current?
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Electric motor. Uses magnetic forces on current-carrying coils to spin.
Electric motor. Uses magnetic forces on current-carrying coils to spin.
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Which part of a simple DC motor reverses the current every half-turn to keep it spinning?
Which part of a simple DC motor reverses the current every half-turn to keep it spinning?
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Commutator (split-ring commutator). Switches current direction to maintain continuous rotation.
Commutator (split-ring commutator). Switches current direction to maintain continuous rotation.
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What is the function of the permanent magnet in many small electric motors?
What is the function of the permanent magnet in many small electric motors?
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It provides a steady magnetic field for the coil to push against. Creates the external magnetic field the coil interacts with.
It provides a steady magnetic field for the coil to push against. Creates the external magnetic field the coil interacts with.
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What is a solenoid in the context of everyday devices?
What is a solenoid in the context of everyday devices?
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A coil that becomes a magnet and can move a metal plunger. Current creates magnetic field to pull/push iron plunger.
A coil that becomes a magnet and can move a metal plunger. Current creates magnetic field to pull/push iron plunger.
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Which device uses an electromagnet to switch a circuit on or off without direct contact?
Which device uses an electromagnet to switch a circuit on or off without direct contact?
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Relay. Small current controls electromagnet to switch larger current.
Relay. Small current controls electromagnet to switch larger current.
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Which common device uses an electromagnet to attract and move a metal armature to make sound?
Which common device uses an electromagnet to attract and move a metal armature to make sound?
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Electric doorbell (or buzzer). Electromagnet pulls striker to hit bell repeatedly.
Electric doorbell (or buzzer). Electromagnet pulls striker to hit bell repeatedly.
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What is the purpose of brushes in a simple DC motor?
What is the purpose of brushes in a simple DC motor?
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They transfer current between the power source and the commutator. Sliding contacts that deliver power to rotating parts.
They transfer current between the power source and the commutator. Sliding contacts that deliver power to rotating parts.
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Identify the direction of the magnetic field between a magnet’s poles: from which pole to which pole?
Identify the direction of the magnetic field between a magnet’s poles: from which pole to which pole?
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From $N$ to $S$ (outside the magnet). Field lines exit north pole and enter south pole.
From $N$ to $S$ (outside the magnet). Field lines exit north pole and enter south pole.
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What is the main difference between a motor and a generator?
What is the main difference between a motor and a generator?
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Motor: electrical to motion; generator: motion to electrical. Motors use electricity to move; generators use motion to make electricity.
Motor: electrical to motion; generator: motion to electrical. Motors use electricity to move; generators use motion to make electricity.
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What is an electromagnet?
What is an electromagnet?
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A magnet made by electric current flowing through a coil. Current through coiled wire creates a controllable magnetic field.
A magnet made by electric current flowing through a coil. Current through coiled wire creates a controllable magnetic field.
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What force causes a current-carrying wire in a magnetic field to move?
What force causes a current-carrying wire in a magnetic field to move?
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A magnetic force on the moving charges in the wire. Lorentz force acts on current perpendicular to field.
A magnetic force on the moving charges in the wire. Lorentz force acts on current perpendicular to field.
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Which action will induce current in a coil: holding a magnet still or moving it into the coil?
Which action will induce current in a coil: holding a magnet still or moving it into the coil?
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Moving the magnet into the coil. Motion creates changing flux; stationary magnets don't induce current.
Moving the magnet into the coil. Motion creates changing flux; stationary magnets don't induce current.
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Identify the energy conversion in an electric motor.
Identify the energy conversion in an electric motor.
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Electrical energy to mechanical (motion) energy. Current in magnetic field creates force that spins the motor.
Electrical energy to mechanical (motion) energy. Current in magnetic field creates force that spins the motor.
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What is electromagnetic induction?
What is electromagnetic induction?
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Producing current in a conductor by changing a magnetic field. Faraday's law: changing magnetic flux induces voltage.
Producing current in a conductor by changing a magnetic field. Faraday's law: changing magnetic flux induces voltage.
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