Electromagnetism & The Motor EffectEdexcel GCSE Physics: Flashcards

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What shape is the magnetic field around a long straight current-carrying conductor?

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What shape is the magnetic field around a long straight current-carrying conductor?: Concentric circles around the wire.
What two factors affect the strength of the magnetic field around a straight conductor?: The size of the current, and the distance from the conductor.
What is a solenoid?: A coil of wire that produces a strong, near-uniform magnetic field along its centre when carrying a current.
Why is the field inside a solenoid strong and uniform?: Because the magnetic fields from each individual coil add together.
Why is the field outside a solenoid weaker?: Because the fields from the individual coils cancel out more outside the solenoid.
What is the motor effect? (higher tier): The force experienced by a current-carrying conductor placed in a magnetic field.
What rule is used to find the directions of force, field and current in the motor effect? (higher tier): Fleming's left-hand rule.
In Fleming's left-hand rule, what does the thumb represent?: The thrust (force).
In Fleming's left-hand rule, what does the first finger represent?: The magnetic field.
In Fleming's left-hand rule, what does the second finger represent?: The current.
State the equation for the force on a current-carrying conductor. (higher tier): F = B × I × l, where B is magnetic flux density, I is current and l is the length of the conductor in the field.
What unit is magnetic flux density measured in?: Tesla (T).
How does an electric motor use the motor effect to rotate? (higher tier, Physics only): Forces act in opposite directions on the two sides of a current-carrying coil in a magnetic field, creating a turning effect that rotates the coil.