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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
QuantityUnit nameUnit 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