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## 11.4 Chapter summary (ESBQH)

Presentation: 243S

• Ohm's Law states that the amount of current through a conductor, at constant temperature, is proportional to the voltage across the resistor. Mathematically we write $$I = \frac{V}{R}$$

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

• We use Ohm's Law to calculate the resistance of a resistor. $$R = \frac{V}{I}$$

• The equivalent resistance of resistors in series ($$R_{s}$$) can be calculated as follows: $$R_{s} = R_{1} + R_{2} + R_{3} + \ldots + R_{n}$$

• The equivalent resistance of resistors in parallel ($$R_{p}$$) can be calculated as follows: $$\frac{1}{R_{p}} = \frac{1}{R_{1}} + \frac{1}{R_{2}} + \frac{1}{R_{3}} + \ldots + \frac{1}{R_{n}}$$

• Electrical power is the rate at which electrical energy is converted in an electric circuit.

• The electrical power dissipated in a circuit element or device is $$P=VI$$ and can also be written as $$P=I^2R$$ or $$P=\frac{V^2}{R}$$ and is measured in joules (J).

• The electrical energy dissipated is $$E=Pt$$ and is measured in joules (J).

• One kilowatt hour refers to the use of one kilowatt of power for one hour.

 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 ($$V$$) Volts $$\text{V}$$

Table 11.1: Units used in electrostatics