Charge and current

Definitions
1. An electric current is the rate of flow of charge. Charge = current * time
  1. Charge is carried by electrons in a circuit.
    1. metals are good conductors as they have free electrons which are able to move. "a sea of free electrons"
  2. will only flow if there's a voltage.
2. Voltage( or potential difference) is the driving force that pushes the current around a circuit
  1. unit = volt, V
3. resistance is something in a circuit that slows the flow of charge down.
  1. measured in ohm.
4. The ammeter
  1. measures the current flowing through the component.
  2. must be placed in series so it's connected to the line with the component.
    1. Voltage- current graphs.
      1. fixed resistor
        filament graph
        as the temperature increases, the resistance increases.
        diode
        current will only flow in one direction.
5. The voltmeter
  1. measures the voltage.
  2. must be placed in parallel around the component. not around the cell or variable resistor.
    1. voltage = current * resistance.
D.C. = direct current.
1. This is provided by cells and bateries.
2. it is a current that flows in one direction
3. Same voltage, same direction = straight line on oscilloscope.
A>C> = Alternating current
1. from mains electricity.
Energy is supplied to the charge at a power source ( such as a cell or battery) .
1. The charge transfers this energy if the voltage drops anywhere throughout the circuit.
  1. The bigger the change in voltage, the more energy is transferred for a given amount of charge.
    1. A battery therefore with a bigger voltage will supply more energy to the circuit for every coulomb of charge because the charge at the start is higher.
2. 1 volt = 1 joule or 1 coulomb
Current is conserved at a junction.
Light dependent resistors.

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Charge and current

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