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Chapter Summary

10.6 Chapter summary (ESCQ2)

Presentation: 27XW

1. Ohm's Law governs the relationship between current and potential difference for a circuit element at constant temperature. Mathematically we write $$I=\frac{V}{R}$$.

2. Conductors that obey Ohm's Law are called ohmic conductors; those that do not are called non-ohmic conductors.

3. Ohm's Law can be applied to a single circuit element or the circuit as a whole (if the components are ohmic).

4. The equivalent resistance of resistors in series ($${R}_{s}$$) can be calculated as follows: $${R}_{s}={R}_{\text{1}}+{R}_{\text{2}}+{R}_{\text{3}}+...+{R}_{n}$$

5. The equivalent resistance of resistors in parallel ($${R}_{p}$$) can be calculated as follows: $$\frac{\text{1}}{{R}_{p}}=\frac{\text{1}}{{R}_{\text{1}}}+\frac{\text{1}}{{R}_{\text{2}}}+\frac{\text{1}}{{R}_{\text{3}}}+...+\frac{\text{1}}{{R}_{n}}$$

6. Real batteries have an internal resistance.

7. 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*}
8. 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 $$\text{V}$$

Table 10.1: Units used in electric circuits