9702 · 20.1
Concept of a magnetic field flashcards
Revision flashcards for Cambridge 9702 Concept of a magnetic field (syllabus 20.1). Flip, recall, then mark a real past-paper question.
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What is a magnetic field?
A region in space where magnetic forces are exerted on other magnets, magnetic materials, or current-carrying wires.
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How do magnetic field lines indicate direction?
They show the path a hypothetical magnetic North pole would follow, originating from North poles and ending at South poles.
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What does the density of magnetic field lines signify?
The magnetic field strength; closer lines mean a stronger field.
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Define Magnetic Flux Density (B).
It's the force per unit current per unit length exerted on a conductor placed perpendicular to the magnetic field. Its unit is the Tesla (T).
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What is the SI unit for Magnetic Flux Density?
The Tesla (T).
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How do magnetic field lines around a long, straight current-carrying wire appear?
As concentric circles centred on the wire.
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Which rule helps determine the direction of a magnetic field around a straight wire?
The Right-Hand Grip Rule.
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What happens to a solenoid's magnetic field when an iron core is inserted?
The magnetic field strength significantly increases because the iron core becomes strongly magnetised.
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Define Magnetic Flux (Φ).
The product of the magnetic flux density and the area normal to the field lines. It represents the total amount of magnetic field passing through a given area.
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What is the SI unit for Magnetic Flux?
The Weber (Wb).
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What is the general formula for the force on a current-carrying conductor in a magnetic field?
$F = BIL \sin(\theta)$, where θ is the angle between the conductor and the magnetic field lines.
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What is the general formula for magnetic flux through an area A?
$\Phi = BA \cos(\theta)$, where θ is the angle between the magnetic field B and the normal to the area A.
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What is the value and name of the constant μ₀?
μ₀ is the permeability of free space, with a value of 4π × 10⁻⁷ T m A⁻¹.
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Do magnetic field lines ever cross?
No, magnetic field lines never cross. The direction of the field at any point is unique.