Electric curcuits cont.

• The current is the same throughout all parts of the circuit.
• Electric circuit

  A flow of charge
• Electric current

  The rate of flow of charge
• Cell or battery

  Produces an electric current by providing electrical potential energy to make charge move
• Voltage or potential difference

  The ability of a cell to produce current
• The circuit must be closed for charge to flow
• Potential difference

  Measured using a voltmeter connected in parallel
• Unit of potential difference

  Volt (V), one volt = one joule per coulomb (J•C-1)
• Electric current is the rate of flow of charge, current needs a closed circuit, current flows everywhere in the circuit
• Series circuit

  • Current is the same everywhere
• Metals

  • Current consists of electrons that flow
• Conventional current

  The flow of positive charge
• Unit of current (I)

  Ampere (A)
• Formula for current

  I = Q/Δt
• Current measurement

  Using an ammeter connected in series
• Electromotive force (emf)

  The maximum energy provided by a battery per coulomb of charge moving through it
• Terminal potential difference

  The voltage measured across the terminals of the battery when current is flowing through the circuit
• Load

  The combined effect of all the items such as light bulbs, resistors that cause charges to do work/transfer energy - known as total resistance
• Conventional current is the flow of positive charge
• The direction of current does not affect the size of current /voltage /readings in a circuit
• Brightness of a bulb is a measure of current strength
• Bulbs in series

  • Current is the same everywhere (identical bulbs are equally bright)
  • The higher the terminal voltage, the brighter the bulb
  • The greater the number of bulbs, the dimmer the bulbs
  • Voltage is split by bulbs in series
• Bulbs in parallel

  • Current is split
  • Potential difference across each path is the same
  • Total current increases when bulbs are added in parallel
• Resistance

  The property of a substance which hinders the flow of charge
• Formula for resistance

  R = V/I
• Factors affecting resistance

  • Type of material
  • Length - the longer the greater the resistance
  • Thickness - the thicker the less the resistance
  • Temperature - the hotter the greater the resistance
• Definition of the unit of resistance, ohm

  If a potential difference of 1V produces a current of 1A then the resistance is 1Ω