Electric circuits term 2

• ELECTRIC CIRCUITS


  • Charge = current x time
  • Parallel resistance = 1 / (1/R1 + 1/R2)
  • Series resistance = R1 + R2
  • Voltage = work / charge
• Electricity


  The process of giving energy to a charge and then using that energy to do work
• Power source


  Gives electrical energy to the charge
• Load


  A device that uses the energy of a charge
• A battery goes "flat" when all of the stored chemical energy in the battery has been converted to electrical energy
• The electrical energy is converted into other forms: heat, light, kinetic, chemical
• Resistance


  Opposition to the flow of electric current
• Ohm's Law


  The current in a conductor is directly proportional to the potential difference across it provided its temperature remains constant
• Emf is the voltage measured across the terminals of a battery when no current is flowing through the battery
• Potential difference (pd) is the voltage measured across the terminals of a battery when current is flowing through the battery
• Series circuits


  • Only one path for current, current is the same everywhere, if broken at any point current stops
• Parallel circuits


  • Current splits into multiple paths, if one branch breaks the others still conduct
• In a series circuit, the voltage is split up across the resistors, with most voltage across the largest resistance</b>
• In a parallel circuit, the current is split up through the resistors, with the current inversely proportional to the resistance
• Current


  The rate of flow of charge
• Potential Difference (V)


  The energy transferred per unit electric charge
• Resistance (R)


  The ratio of potential difference across a resistor to the current through it
• The coulomb (C) is that quantity of charge which passes a fixed point in a conductor in one second when the conductor carries a current of one ampere
• Emf


  The voltage measured across the terminals of a battery when no current is flowing through the battery
• Potential difference (pd)


  The voltage measured across the terminals of a battery when current is flowing through the battery
• Ohm's Law states that the current in a conductor is directly proportional to the potential difference across it provided its temperature remains constant
• Resistance of a material is dependent on the type of material, as well as the length, thickness and temperature of the conductor
• Resistors in series


  • Current is the same through each resistor
  • Voltage is split up across resistors. The voltage is directly proportional to the resistance in the series combination
  • 'Voltage divider'
  • Eg. Dimmer switches
• Resistors in parallel


  • Current is split up through resistors. The current is inversely proportional to the resistance. The smaller resistance, the more current going through it
  • Voltage is the same across each resistor in the parallel combination
  • 'Current divider'
  • Eg Cars, houses
• Combination circuits


  1. Identify the separate series and parallel combinations in the circuit

  2. Apply Ohms Law consistently to each resistor, or each combination of resistors or the whole circuit