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Ohm's Law
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The potential difference V across a device is given by its resistance R and the current I that flows through it |
Resistance of a wire
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The resistance R of a length L of wire with a cross-sectional area A and resistivity ρ. Resistivity has units Ω⋅m. |
Electric power
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With help from Ohm’s law, electric power P can be calculated using any combination of two of the following quantities: resistance R, voltage V or current I |
RMS voltage and current (AC circuits)
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The root-mean-square values can be calculated from the peak values (V0 and I0) and are used to calculate the average power P in AC circuits: P=IRMS2R=(VRMS2)/R |
Resistances in series
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For more than two resistances in series: Req=R1+R2+R3+R4... |
Resistances in Parallel
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For more than two resistances in parallel: (1/Req)=(1/R1)+(1/R2)+(1/R3)+... |
Capacitance
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A higher capacitance capacitor can store more charge at the same voltage. |
Capacitors in series CS and
parallel CP
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For more than two capacitors: (1/Cs)=(1/C1)+(1/C2)+(1/C3)+... CP=C1+C2+C3+C4+... |
Electric energy stored by a
capacitor
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Amount of electric energy stored in a capacitor is given in terms of the capacitance C and the potential difference between the conductors V. |