Physics - 4 - Current electricity


4.1 Electrical charges

  • Certain insulating materials become charged when rubbed together
  • Electrons are transferred when objects become charged: -Insulating materials that become positively charged when rubbed lose electrons -Insulating materials that become negatively charged when rubbed gain electrons
  • Like charges repel; unlike charges attract
  • Have you ever stuck a balloon on a celing? All you need to do is rub the balloon on your clothing before you touch it on the ceiling. The rubbing action charges the balloon with static electricity. In other words, the balloon becomes electrically charged.
  • -Adding electrons to an uncharged atom makes it negative (because the atom then has more electrons than protons) -Removing electrons from an uncharged atom makes it positive (because the atomn has fewer electrons than protons)

Electric circuits

  • Every component has its own agreed symbol. A circuit diagram shows how components are connected together
  • A battery consists of two or more cells connected together
  • The size of an electric current is the rate of flow charfe
  • Electric current = charge flow
  •                           time taken
  • An electric current is a flow of charge. When an electric torch is on, millions of electrons pass through the torch bulb and through every cell every second. Each electron carries a negative charge.


  • The potential difference across a component (volts) = work done or energy transferred


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