ElectromagnetismAQA GCSE Physics: Flashcards

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What is produced around a wire when a current flows through it?

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What is produced around a wire when a current flows through it?: A magnetic field, forming concentric circles around the wire.
What two factors affect the strength of the magnetic field around a current-carrying wire?: The size of the current (larger current = stronger field) and the distance from the wire (closer = stronger field).
What is a solenoid?: A wire wound into a coil, used to create a stronger, more uniform magnetic field than a straight wire.
How do you turn a solenoid into an electromagnet?: Place an iron core inside it — the iron core concentrates and strengthens the magnetic field.
What is the key advantage of an electromagnet over a permanent magnet?: It can be switched on and off (and its strength varied) by controlling the current.
What is the motor effect?: The force produced on a current-carrying conductor when it is placed in a magnetic field.
State Fleming's left-hand rule.: First finger = Field, seCond finger = Current, THumb = Thrust (force/motion).
Give the equation for the force on a current-carrying conductor in a magnetic field.: F = BIl, where F is force (N), B is magnetic flux density (T), I is current (A), l is length in the field (m).
When is the force on a current-carrying conductor in a magnetic field at its maximum?: When the conductor is at right angles (90°) to the magnetic field.
What happens to the force if the current in a conductor is reversed?: The direction of the force reverses.
What causes a current-carrying coil in a magnetic field to rotate?: Forces (from the motor effect) act in opposite directions on opposite sides of the coil, creating a turning effect.
How does a moving-coil loudspeaker produce sound?: An alternating current in a coil sitting in a magnetic field experiences a varying force (motor effect), vibrating an attached cone, which creates sound waves in the air.
What unit is magnetic flux density measured in?: Tesla (T).
What is the name for a switch that is operated by an electromagnet?: A relay.