Electrical quantities

4.2 Electrical charge

undefined Electric circuits

Electrical quantities

  1. Current

    1. Current is the flow of charge
    2. I = Qt
    3. An ammeter is wired in series in a circuit to measure the current in that area
    4. The direction of flow of electrons is the opposite of the flow of conventional current, since current is the flow of positive charge and electrons are negatively charged

  2. Potential difference (voltage)

    1. The potential difference across a circuit component is measured in volts
    2. A voltmeter is wired in parallel to a component to measure the potential difference across it

  3. Electromotive force

    1. The e.m.f. of a source of electrical energy is measured in volts
    2. The e.m.f. is defined in terms of energy supplied by a source in driving charge round a complete circuit

  4. Resistance

    1. Resistance is potential difference divided by current
    2. V = IR
    3. The resistance of component can be obtained experimentally by wiring a voltmeter in parallel with it and an ammeter in series with it and dividing the measured voltage with the current
    4. The resistance of a wire is directly proportional to its length and inversely proportional to its cross-sectional area

  5. Electrical energy

    1. P = IV & E = IVt 1
  1. Derivation: P = Et = Qt⋅EQ = IV ↩