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31 Cards in this Set
- Front
- Back
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Current |
Rate of flow of charge |
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Formula for current |
I=Q/t |
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Voltage (potential difference) |
Energy converted per unit charge |
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Formula for voltage |
V=W/Q |
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In a series circuit, current... |
...is the same all the way round the circuit. |
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In a parallel circuit, current... |
...is split between the branches. |
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In a series circuit, voltage... |
...is split between the components. |
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In a parallel circuit, voltage... |
...is the same across each branch. |
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Work done by the charge carriers in a circuit |
W=VIt |
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Electrical power |
P=IV |
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Resistance |
The voltage required per current flow in the circuit |
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Formula for resistance |
R=V/I |
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Cause of resistance |
Collisions between charge carriers in the material with each other and with the fixed positive ions of the material. |
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Ohm's law |
The pd across a metallic conductor is directly proportional to the current through it, provided the physical conditions do not change. |
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an Ohmic conductor is... |
...a conductor which obeys Ohm's law. |
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Resistivity |
A property of a material which determines its resistance. |
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Formula for resistivity |
ρ=(RA)/L |
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Unit of resistivity |
Ohm metre |
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A superconductor has... |
zero resistivity at and below its critical temperature |
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At any junction in a circuit, the total current... |
...leaving the junction is equal to the total current entering the junction |
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In series, the current entering a component... |
...is the same as the current leaving the component |
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Total resistance of resistors in series |
R=R1+R2+R3+... |
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Total resistance of resistors in parallel |
1/R=1/R1+1/R2+1/R3+... |
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Alternative formulae for power |
P=I^2R or P=V^2/R |
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Rate of heat transfer |
I^2R |
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Energy transferred to object by current in time t |
I^2Rt |
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Emf |
ɛ=E/Q, is the electrical energy per unit charge produced by the source. |
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Internal resistance |
r, is the loss of potential difference per unit current in the source when current passes through the source. |
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Formula for emf |
ɛ=I(R+r) i.e. the Terminal pd + the Lost pd |
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Power supplied by the cell |
I^2R+I^2r |
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Power delivered to external resistance |
(ɛ^2/(R+r)^2)R |
