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• Circuit Symbols


  • Battery
  • Voltmeter
  • Ammeter
  • Lamp
  • Resistor
• Battery


  Made up of one or more cells
• Voltmeter


  Measures the voltage across the battery terminals, measured in volts (V)
• Ammeter


  Measures the size of the electrical current, measured in Amps (A)
• Lamp


  Converts electrical energy to light, the greater the current the brighter the bulb
• Resistor


  Reduces the flow of current, the greater the resistance the lower the current
• Conductors


  • Materials which allow electrical current to flow through them easily, metals are generally good electrical conductors
• Insulators


  • Materials which are poor conductors and do not allow electrical current to flow through them easily, most non-metals like plastic, glass and rubber are good insulators
• Electrical conductivity


  Depends on the number of free electrons in the material
• Circuits and current


  1. Electric current will only flow through a complete circuit

  2. Chemical reaction inside the battery pushes the current from the negative terminal to the positive terminal

  3. Current is defined as a flow of electrical charge

  4. The more electrons flow through a wire each second, the greater the current

  5. Units of current are amperes, often shortened to amps
• Voltage


  The amount of energy transferred by each unit of charge passing between two points of a circuit, the unit is the volt
• The greater the voltage in a circuit


  The more current will flow and the brighter will be a bulb
• Series circuits


  • No branches and only one loop
  • If a lamp breaks or a component is disconnected, the circuit is broken and all the components stop working
  • If you put more lamps into a series circuit, the lamps will be dimmer than before
• Parallel circuits


  • Branches and more than one loop
  • If a lamp breaks or a component is disconnected from one parallel wire, the components on different branches keep working
  • The lamps stay bright if you add more lamps in parallel
  • Switches can be added to a parallel circuit to turn components on and off
• Resistance


  • Causes the filament to heat up and electrical energy is changed into heat and light energy
  • Measured in ohms which has the symbol (Ω)
  • The greater the resistance of the resistor the lower the current that will flow in the circuit
• If you add more bulbs into a series circuit

  The resistance in the circuit will increase and so the current is less
• Variable resistor


  • Resistance can be altered, used in a dimmer switch
• LDR (light dependent resistor)


  • Resistance decreases when more light is shone upon it
• Thermistor


  • Resistance decreases when it is heated
• A wire's resistance


  Increases as it gets hot
• Forces


  Can speed up or slow down objects or change their shape or direction
• Unit of force


  Newtons (N)
• Force meters


  Contain a spring connected to a metal hook, the spring stretches when a force is applied to the hook, the bigger the force the longer the spring stretches
• Types of forces


  • Thrust
  • Weight
  • Tension
  • Friction
  • Air resistance
  • Drag
  • Upthrust
  • Normal force
  • Magnetism
  • Electrostatic
• Contact forces


  Forces that need to be touching to be felt, e.g. friction
• Non-contact forces


  Forces that can act over a distance, e.g. gravity
• Force diagram


  • Shows the size of the force (longer arrow = bigger force)
  • Shows the direction the force acts
• Balanced forces


  Two forces acting on an object that are equal in size but act in opposite directions
• Resultant force


  The size of the overall force acting on an object
• Mass


  The amount of substance or 'matter' an object contains, measured in kilograms (kg)
• Weight


  The force of gravity pulling on a mass, measured in newtons (N)
• On Earth, g has a value of 10 N/kg
• On the Moon


  Your mass would not change, but your weight would be less than on Earth because the Moon's gravity is weaker
• Friction


  A force that stops two surfaces sliding past each other, caused by tiny bumps on the surfaces
• Useful friction


  • Grip for shoes and tyres
  • Brakes on bicycles and cars
  • Holding a cup of orange juice
• Problems caused by friction

  • Slows down moving machinery
  • Can make machinery overheat
• Drag


  The force that slows objects down as they move through air or water
• The faster an object moves


  The greater the air resistance
• Hooke's Law


  The extension of a spring is directly proportional to the force (weight) applied, provided the limit of proportionality is not exceeded
• Floating and sinking


  If the upthrust is bigger than the weight of an object it will float, if the upthrust is smaller than the weight of an object it will sink