Electricity - topic 2

• For charge to flow in a circuit:

  • The circuit must be closed (no open switches)
  • There must be a source of potential difference (battery/cell)
• Current is the flow of electrical charge, and the greater the rate of flow of charge, the greater the current
• In a single closed loop, the current has the same value at any point
• The current through a component depends on both the resistance (R) of the component and the potential difference (V) across the component
• The greater the resistance of a component, the smaller the current for a given potential difference across the component
• The relationship between current (I), potential difference (V), and resistance (R) can be calculated using the equation: V = IR
• If the resistance of components like lamps, diodes, thermistors, and LDRs is not constant, the graph of current against potential difference is nonlinear
• Resistance decreases with temperature in thermistors, and increases with light intensity in LDRs
• Mains electricity in the UK is an AC supply with a frequency of 50 Hz and about 230 V
• In a plug, there are 3 wires: live wire (brown), neutral wire (blue), and earth wire (green and yellow stripes)
• Power is the energy transferred per second and is directly proportional to current and voltage
• The National Grid is a system of cables and transformers linking power stations to consumers across the UK
• Insulators do not conduct electricity as their electrons are fixed, while conductors can conduct electricity as their electrons can flow
• Static electricity occurs when two insulators are rubbed together, transferring electrons and creating positive and negative charges
• Closer to the charge, the stronger the force felt in an electric field