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25 Cards in this Set
- Front
- Back
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What happens to materials as they cool down? |
Resistance decreases, current increases, and resistivity decreases |
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What is superconductivity? |
Superconductivity is when a material has zero resistance when cooled below its critical temperature |
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What is zero kelvin? |
The temperature at which the particles have no movement (absolute zero) = -273 degrees centigrade |
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What is a superconductor? |
A superconductor is a wire/device that has zero resistivity at and below its critical temperature |
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What is critical temperature? |
Critical temperature is the temperature at which the electrical resistivity of the cuperconductor drops to zero |
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What happens when a superconductor's temperature is raised above critical? |
The superconductor will lose its superconductivity |
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What is the equation for power dissipated in a d.c. circuit? |
P = I^2 x R |
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What is root mean square? |
The equivalent alternating current that will result in the same heating as in direct current |
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What heats a component? |
Current and voltage |
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What is the equation for the root mean square of an alternating current or p.d? |
1 / √2 x the peak value |
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What is the equation for power in an a.c. circuit? |
P = Irms / √2 x Vrms |
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What does a potential divider consist of? |
Two or more resistors in series with each other and with a source of fixed potential difference |
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What can a potential divider be used for? |
To supply a pd which is fixed at any value between zero and the source pd to supply a variable pd |
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What is the equation for the pd across each resistor in series with the cell? |
Current x resistance of each resistor |
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What is the advantage of a potential divider? |
The advantage of using a potential divider is that the current through the component and the pd across it can be reduced to zero |
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What is a potential divider? |
A potential divider varies the pd from zero |
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What is the equation for the power supplied by the cell? |
I x emf = I^2 x R + I^2 x r |
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What is internal resistance |
The IR of a source is the loss of pd per unit current in the source when current passes through the source |
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What is the equation for emf? |
emf = Energy transferred / Charge |
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When in series, what happens to the pd across two or more components? |
The pd across all components is equal to the sum of the p.d(s) across each component |
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What is the equation for the rate of heat transferred? |
I^2 x R |
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What is emf? |
Electromotive force of the source is the electrical energy per unit charge produced by the source |
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What happens to current at any point in the circuit? |
The total current entering the junction is equal to the total current leaving the junction |
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When in series, what happens to the current through one or more components? |
The current passing through two or more components in series is the same through each component |
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What is velocity? |
The change of displacement over time |
