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5 Cards in this Set
- Front
- Back
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Magnetic field
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Magnitude - magnetic flux density
Magnitude & direction -symbol: B, units: tesla (T) Direction = direction a north pole would be pushed Field lines: closer together = stronger field, crosses (x) = field into page, dots (.) = field out of page |
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Magnetic field around a straight current carrying wire
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Circular magnetic field
Direction can be found with right hand grip rule: thumb=direction of conventional current, fingers curl in direction of magnetic field |
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Solenoid
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A coil of wire carrying a current.
Produces a magnetic field similar to a bar magnet. Strength depends on: number of coils/loops, current, 'core' material (iron or similar rod placed inside coil) Magnetic field is strongest inside/ RHG rule: fingers curl in direction of current, thumb points towards N pole, and in direction of field inside |
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Force on a current carrying wire
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Current carrying wire placed inside a magnetic field will experience a force.
If current is perpendicular to field directions, F=BIl. Direction-RHP: fingers in direction of magnetic field, thumb in direction of current, palm moves in direction of force Not perpendicular: F=BIlsinθ Parallel: θ=0, F=0 |
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Purpose of the split-ring commutator
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To change the direction of current through the coil every half rotation, so that it continues to rotate constantly in one direction, by reversing the force direction on each side of the coil
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