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31 Cards in this Set
- Front
- Back
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Current definition |
Rate of flow of charge |
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Current units |
Amps, A |
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Resistance definition |
Anything that slows the flow of charge down |
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Potential difference definition |
Energy transferred per charge passed |
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Resistance unit |
Ohms |
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Potential difference unit |
Volt, V |
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Equipment used to measure current |
Ammeter |
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Equipment used to measure potential difference |
Voltmeter |
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Factors affecting resistance required practical |
- Set up a circuit an ammeter in series, a voltmeter in parallel to the ruler and crocodile clip wires and a switch connected to a cell - Attach a crocodile clip at 0 cm and the other end at 10 cm. - Record this length - Close the switch and record the current and potential difference across the wire - Open the switch - repeat with different lengths of wire - use V/I = R to find the resistance - plot a graph with these result with resistance on the y and length of wire on the X - draw a line of best fit. This should go through the origin - This should go through the origin - the independent variable is the length of wire - the dependant variable is the resistance - the control variables are the wire, the cell, the crocodile clips, the temperature of the wire etc |
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LDR and how it works |
Light dependant resistor, when the light is bright, there is a low resistance, when it is low, there is a high resistance. These are used in night lights |
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Thermistor and how it works |
Thermistors rely on the temperature. In a hot environment, it has a low resistance. In a cold environment, it has a high resistance These are used in thermostats and cars |
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What happens to current, potential difference, and resistance is a series circuit? |
Current is the same everywhere Potential difference is shared Resistance is added up |
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What happens to current, potential difference in a parallel circuit? |
Current is shared Potential difference is the same all over |
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What happens when a resistor is added in parallel? |
It reduces the total resistance |
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What type of current is battery? |
Direct current |
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What type of current is mains? |
Alternating current |
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What is the potential difference in the mains? |
230V |
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What is the blue wire and what does it do? |
Neutral wire - completes the circuit, is a t 0V |
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What is the brown wire and what does it do? |
Live wire - provides alternating potential difference from the mains |
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What is the green and yellow wire and what does it do? |
Earth wire - stops the casing becoming live and only carries a current when there is a fault. This is at 0V |
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What is the national grid? |
A giant system of cables that connects power stations to consumers |
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What is the potential difference of the national grid? |
400000V |
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Why does the current need to be lowered in the national grid? |
Because there is lots of heat loss with a high current but not with a high potential difference, so turning the current down reduces waste energy |
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How is the potential difference changed? |
Through transformers |
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What is a build up ofstatic electricity caused by? |
Friction |
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What is the name of the rod that is positively charged in relation to static electricity? |
Acetate rod |
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What is the name of the rod that is negatively charged in relation to static electricity? |
Polythene rod |
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What moves to create a static charge? |
Electrons NOT positive charges |
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What happens when there is too much static? |
A spark occurs because the electrons jump from a high potential difference ( the material) to a low potential difference (the ground) |
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What do electric charges make? |
An electric field |
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What do step up and step down transformers do? |
Increase and lower the potential difference and current so the national grid is more efficient |
