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28 Cards in this Set
- Front
- Back
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Define electric current? |
A flow of charge in A |
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In an electric current... |
The components/wires are full of charges that are free to move Battery causes free charges to move The charges aren't used up but flow in a continuous loop |
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What do metals contain and what does it allow? |
Free electrons in their structure Which move to create an electric current |
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Light dependent resistor |
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Fixed resistor |
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Variable resistor |
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Thermistor |
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Define direct current? |
Flows in same direction |
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Define alternating current? |
Changes direction of flow back and forth Used for mains electricity |
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Why is a.c. used instead of d.c.? |
Easier to generate Distributed more efficiently Only a.c. can be used in a transformer |
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What happens when you add more batteries in parallel? |
Total potential difference and current remain the same Each battery supplies less current |
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The greater the resistance in a circuit... |
The smaller the current will be |
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What happens when you add more resistors in parallel? |
Resistance reduces Current increases |
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What occurs when the current flow? |
Moving charges collide with the vibrating ions in the wire... Therefore giving them energy The increase in energy causes the component to heat up Makes filament glow- light energy |
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Resistance formula? |
Resistance(ohms)= Voltage(V) --------------- Current(A) |
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What does the resistance of a thermistor depend on? |
Temperature |
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(Thermistor) As the temperature increases... |
Its resistance decreases More current flows |
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What does the resistance of an LDR depend on? |
Light intensity |
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(LDR) As the amount of light falling on it increases... |
Its resistance decreases More current flows |
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What happens when you move a magnet into a coil of wire? |
A voltage is induced between the ends of the wire... Because the magnetic field is being cut |
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How can a current be induced in the opposite direction? |
Moving the magnet out of the coil Moving the other pole into the coil |
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Define generator? |
A device in which a magnet spins inside a coil of wire... To produce a voltage or an electric current Produces mains electricity Produces a.c. |
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How can the size of the induced voltage be increased? |
Increase the speed of rotation of the magnet Increase strength of magnetic field Increasing the number of turns on the coil Placing an iron core inside the coil |
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Power formula? |
Power(W)= Voltage(V) x Current(A) |
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Define transformer? |
A device used to change the potential difference / voltage of an a.c. Consist of 2 coils of wire- primary coil - secondary coil Wrapped around a soft iron core |
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Transformer equation |
Voltage on primary coil No. of turns on primary coil --------------------------------------= ----------------------- Voltage on secondary coil No/ of turns on secondary coil |
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Define electric motor and its forces? |
Consists of a coil of wire that rotates between the opposite poles of a permanent magnet... When a current flows through the coil The thrust will be at right angles to both the current direction and the lines of the magnetic field Commutator is a rotary switch that turns with the coil |
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Ways a motor is used: |
DVD- rotates disk so info can be read Washing machine- rotate drum and agitate the wash Tumble dryer- To rotate the drum and provide uniform heat Microwave oven- to rotate food so it is evenly heated |
