11871139
Description
Flashcards by Victoria Heath, updated more than 1 year ago
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Created by Victoria Heath
almost 7 years ago
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| Question | Answer |
| When is a magnetic field produced around a wire? | It occurs when an electric current flows in a wire. |
| What are the three ways in which we can strengthen the magnetic field around a wire? | wrapping coil around iron core - adding more turns to coil - increase current flowing in coil |
| What two things are needed to produce an electric current? | A magnet and a coil of wire |
| What is electromagnetic induction? | When a magnet moves into a coil of wire, producing voltage. |
| Give two ways the direction of voltage can be reversed. | - the magnet is moved out of the coil - other pole of magnet is moved into the coil |
| When only is voltage produced? | When the magnet is moving inside the coil. |
| What do field line patterns show? | The direction and shape of a magnetic field. |
| What are field line patterns usually drawn with? | A plotting compass |
| What do the arrows on field line diagrams represent? | The direction from North to South poles. |
| What is a solenoid? | A long thin spiral of wire used to make magnetic fields. |
| How do you increase the induced voltage? | - move magnet faster - add more turns to coil - increase strength of magnet |
| Define the motor effect. | When a current carrying wire or coil exerts a force upon a permanent magnet or another wire/coil. |
| How can a simple electric motor be constructed? | Using a coil of wire which can freely rotate between two opposing magnetic poles. |
| Explain how a motor works. | When electric current flows through the coil, it experiences a force and moves. |
| What must be done to prevent the coil coming to a halt? | The direction of current must be changed every half turn using a conducting ring split in two - also known as a split ring or commutator. |
| What do speakers contain both of? | A permanent magnet and an electromagnet. |
| Explain how a speaker works. | 1) Electric current from amplifier is continually changing direction, which causes the magnetic field around the electromagnet to also continually change. 2) This causes the electromagnet to move back and forth. 3) Then, the speaker cone vibrates back and forth which generates sound waves. The frequency of these sound waves is determined by the frequency at which the current changes direction. |
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