103202
Description
Flashcards by zolas_horses, updated more than 1 year ago
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Created by zolas_horses
over 11 years ago
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| Question | Answer |
| Explain the direction that the coil will rotate inside the magnetic field, when a d.c. current is flowing in the coil? | The coil will rotate in a clockwise motion, because using Fleming's left hand rule, I know that when the current flows (North to South) away from the South pole end, the coil will be turned up. Then the current is reversed by the commutator the other side and will be forced upwards. |
| What happens if the number of turns on the primary is greater than that of the secondary? | The voltage on the primary will also be greater than that of the secondary and vice versa. |
| What is the name given to a transformer where the secondary voltage is less than the primary voltage? | A step down transformer |
| What is the name given to a transformer where the primary voltage is less than the secondary voltage? | Step up transformer |
| If a voltage between a primary to secondary coil increases what happens to the current? | It decreases |
| Why do step down transformers have thin primary coil wires but thick secondary coil wires? | Because current is increased in a step down transformer and bigger currents need a thicker wire. |
| What is a magnetic field? | A magnetic field is a space where magnetic materials experience force. |
| How do we represent the magnetic field? | Field diagrams |
| What ways do the arrows always point on field lines? | North to South |
| Explain the generation of electricity using a magnet and a coil? | -The current flows when magnetic field lines are ''cut'' - The faster they are ''cut'' the more current - The direction they are ''cut'' affects the current direction |
| What happens when a magnet causes current to flow in wires? | Magnetic induction |
| How is the induced current increased with a magnet and wire? | -You can increase the number of coils/number of coil turns, which in turn increases the amount of times the magnetic field lines are ''cut'' which increases current. -Stronger magnets or faster movement (of the magnet) also increases the current |
| Moving a wire through a magnetic field has a voltage induced which in turn causes what to be induced? | A current |
| How can the induced current in a wire through a magnetic field be increased? | -Speed of movement -Strength of magnetic field - More wires |
| How do we determine the direction in which the current will flow in the wire? | Fleming's right hand rule (Generators) |
| Which finger represents what in Fleming's right hand rule? | 1st finger - Field 2nd finger - Current Thumb - Movement |
| How is the current in a generator supplied to an external circuit? | The coil is rotated between the poles of a magnet. The slip rings are fixed to the coil and turn around with it. The two carbon contacts rub against the slip rings as the coil is rotated so that the generated current is fed to the external circuit. |
| Why is an alternating current generated? | The sides of the coil move up and through the field lines the down through them each time it rotates once. The changing motion direction means a change in the current direction. |
| What rule do we use for motors? | Fleming's left hand rule |
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