8703543
Description
Flashcards by david doran, updated more than 1 year ago
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Created by david doran
almost 7 years ago
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| Question | Answer |
| How is a magnetic field formed in a wire ? | When a current flows through a wire a magnetic field is produced around the wire. |
| What is the motor effect ? | A simple electric motor can be built using a coil of wire that is free to rotate between two opposite magnetic poles. When an electric current flows through the coil, the coil experiences a force and moves. This is called the motor effect. |
| How can the size and force of the motor effect be increased ? | The size of the force can be increased by: ■ increasing the strength of the magnetic field ■ increasing the size of the current. |
| in which circumstance will a conductor not experience a force in a magnetic field ? | The conductor will not experience a force if it is parallel to the magnetic field |
| How can you reverse the direction of force in an electric motor ? | The direction of the force is reversed if either the direction of the current or the direction of the magnetic field is reversed. |
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Explain how an electric bell works
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When the current flows through the circuit, the electromagnet makes a magnetic field. The electromagnet attracts the springy metal arm. The arm hits the gong, which makes a sound. The circuit is broken now the arm is out of position. The electromagnet is turned off and the springy metal arm moves back. The circuit is complete again. The cycle repeats as long as the switch is closed. |
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Explain how a circuit breaker works
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The circuit breaker does the same job as a fuse, but it works in a different way. A spring-loaded push switch is held in the closed position by a spring-loaded soft iron bolt. An electromagnet is arranged so that it can pull the bolt away from the switch. If the current increases beyond a set limit, the electromagnet pulls the bolt towards itself, which releases the push switch into the open position |
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Explain how a loudspeaker works ?
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1.(the current flowing through the coil) creates a magnetic field (around the coil) (this magnetic field) interacts with the permanent magnetic field 2. this produces a (resultant) force (and coil / cone moves) 3. when the direction of the current changes, the direction of the force changes to the opposite direction 4. In turn, the speaker cone vibrates back and forth, which generates sound waves. |
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