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20 Cards in this Set
- Front
- Back
What do all electric currents in a wire produce?
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A circular magnetic field
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How does the right hand grip rule work for a wire?
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Thumb points in direction of current and fingers curl in direction of field (N to S)
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How do you increase the strength of a magnetic field around a current carrying wire?
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Inc current
Wrapping wire into solenoid Using thicker wire |
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How do you make a solenoid?
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Wrap insulated wire into a coil making the field stronger
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How does the right hand grip rule for solenoids work?
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Right hand fingers curl in current direction and thumb points north
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How do you increase the strength of a field in a solenoid?
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Inc current
Thicker wire Inc number of coils Wrap around magnetically soft core |
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What is an electromagnet
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A coil of wire wrapped around a magnetically soft core
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Advantages of electromagnet over permanent?
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Can be switched on and off
Strength can be increased by inc number of turns and inc current |
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How do you predict force in magnetic fields?
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Flemings left hand rule
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Explain flemings left hand rule
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Force in thumb
Field from first finger (N to S) Current in second finger (+ve to -ve) |
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Explain the motor effect
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Any charged particle in a magnetic field experiences a force providing it isnt moving parallel to the magnetic field.
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Why does the motor effect happen?
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The magnetic field produced by the charged particle interacts with the magnetic field of the magnet.
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How do you increase the force in a wire?
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Inc current
Increase magnetic field strength |
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Describe how a loudspeaker works
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The current flowing through the coil is at 90° to the magnetic field.
It experiences a force (right or left) This moves the cone With an AC current, the direction reverses, reversing the force direction This happens many times a second causing the cone to vibrate, producing a sound with the same frequency as the AC current producing it. |
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Larger current in a loudspeaker =
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larger force, greater movement of cone and louder sound
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Increasing AC frequency in a loudspeaker...
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Increases the pitch
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Describe how a DC motor uses the principles from the motor effect.
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The magnetic field produced by the current interacts with the magnetic field of the magnet producing a force which acts on the wire making it move.
It rotates because current flowing in opposite directions in parallel wires produces forces in opposite directions and these are not in the same straight line. One side experiences upward force and the other side downward. The coil rotates and after 90° the commutator halves swap contact from one brush to the other. This reverses the current through the coil, reversing the forces on each side, continuing rotation. Without the commutator the coil would stay in a vertical position, with equal forces acting in opposite positions. |
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How do you increase the rotation speed of a motor
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Increasing magnetic field strength (coil is wound onto soft iron armature)
Increasing number of turns Increasing the current |
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What material would you use for the brushes of the commutator?
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Carbon
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What effect does a larger mass have on the acceleration of force produced?
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The higher the mass of an object, the smaller the acceleration the force will produce.
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