10.6 Chapter summary
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10.6 Chapter summary (ESCQ2)
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Ohm's Law governs the relationship between current and potential difference for a circuit element at constant temperature. Mathematically we write \(I=\frac{V}{R}\).
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Conductors that obey Ohm's Law are called ohmic conductors; those that do not are called non-ohmic conductors.
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Ohm's Law can be applied to a single circuit element or the circuit as a whole (if the components are ohmic).
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The equivalent resistance of resistors in series (\({R}_{s}\)) can be calculated as follows: \({R}_{s}={R}_{\text{1}}+{R}_{\text{2}}+{R}_{\text{3}}+...+{R}_{n}\)
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The equivalent resistance of resistors in parallel (\({R}_{p}\)) can be calculated as follows: \(\frac{\text{1}}{{R}_{p}}=\frac{\text{1}}{{R}_{\text{1}}}+\frac{\text{1}}{{R}_{\text{2}}}+\frac{\text{1}}{{R}_{\text{3}}}+...+\frac{\text{1}}{{R}_{n}}\)
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Real batteries have an internal resistance.
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The potential difference \(V\) of the battery is related to its emf \(\mathcal{E}\) and internal resistance \(r\) by:
\begin{align*} \mathcal{E}& = V_{\text{load}} + V_{\text{internal resistance}}\\ &\text{or} \\ \mathcal{E}& = IR_{Ext} + Ir \end{align*} -
The external resistance in the circuit is referred to as the load.
Physical Quantities | ||
Quantity | Unit name | Unit symbol |
Current (\(I\)) | Amperes | \(\text{A}\) |
Electrical energy (\(E\)) | Joules | \(\text{J}\) |
Power (\(P\)) | Watts | \(\text{W}\) |
Resistance (\(R\)) | Ohms | \(\text{Ω}\) |
Voltage / Potential difference (\(V\)) | Volts | \(\text{V}\) |
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10.5 Extension: Wheatstone bridge [Not examinable]
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