Static electricity

• Source: 'Quote'
• Edexcel IGCSE Physics
• 2.4 Static Electricity
• 2.4.1 Conductors & Insulators

  • Conductors
  • Insulators
  • Electrons
• Conductors

  • Material that allows charge (usually electrons) to flow through it easily
  • Examples: Silver, Copper, Aluminium, Steel
  • Tend to be metals
  • Made up of positively charged metal ions with delocalised outermost electrons
• Insulators

  • Material that has no free charges, hence does not allow the flow of charge through them very easily
  • Examples: Rubber, Plastic, Glass, Wood
  • Some non-metals allow some charge to pass through them in the form of static electricity
• Core Practical: Investigating Charging by Friction

  1. Aim of the Experiment: Investigate how insulating materials can be charged by friction

  2. Variables: Independent variable = Rods of different material, Dependent variable = Charge on the rod, Control variables: Time spent rubbing the rod, Using the same type of cloth, Using the same length of rod

  3. Equipment List

  4. Method

  5. Analysis of Results
• Analysis of Results

  1. When two insulating materials are rubbed together, electrons will pass from one insulator onto the other insulator

  2. Polythene rod is given a negative charge by rubbing it with the cloth because electrons move from the cloth to the rod, making the rod negatively charged
• Electrons will pass from one insulator onto the other insulator


  Electrons move from the cloth to the polythene rod
• Charging by friction

  When certain insulating materials are rubbed against each other, they become electrically charged
• Charges remain on the insulators and cannot immediately flow away
• One material becomes positive and the other negative


  An example is a plastic or polythene rod being charged by rubbing it with a cloth
• A polythene rod may be given a charge by rubbing it with a cloth
• Electrons are transferred to the polythene rod while they move from the acetate rod
• If the material is repelled (rotates away) from the polythene rod


  Then the materials have the same charge
• If the material is attracted to (moves towards) the polythene rod


  Then they have opposite charges
• This experiment can be carried out in several different ways
• To improve the outcome of the experiment, consider investigating a variable with a numerical result
• For example, the independent variable could stay the same (using rods of different material)
• The dependent variable could change to be the number of paper circles picked up by each rod
• With numerical data, more analysis can be carried out e.g. creating a graph or a chart
• Better conclusions can be drawn e.g. the rod made of ___ picked up more circles of paper than the other rods, therefore it became the most charged
• When charging by friction, only the electrons can move, not any 'positive' charge, therefore if an object gains a negative charge, something else must have gained a positive charge
• The charge of a particle can be positive, negative, or neutral (no charge)
• Electrons are negatively charged particles, protons are positive, and neutrons are neutral
• In a neutral atom, the number of electrons is equal to the number of protons
• The number of negative electrons in an atom balances the number of positive protons
• An object becomes negatively charged when it gains electrons and positively charged when it loses electrons
• The number of electrons is equal to the number of protons
• The equal (but opposite) charges cancel out to make the overall charge of the atom zero
• An object becomes negatively charged when it gains electrons

  Positively charged when it loses electrons
• Two charged particles or objects close together exert a force on each other


  Force could be attractive (objects get closer together) or repulsive (objects move further apart)
• Whether two objects attract or repel depends on their charge

  If charges are opposite, they will attract. If charges are the same, they will repel
• Opposite charges attract, like charges repel
• Attraction and repulsion between two charged objects are examples of a non-contact force
• Materials only become positively charged because of the loss of electrons, rather than the 'gain' of any positive charge
• All objects are initially electrically neutral, meaning the negative (electrons) and positive charges are evenly distributed
• When electrons are transferred through friction, one object becomes negatively charged and the other positively charged
• The object to which the electrons are transferred becomes negatively charged
• The object from which the electrons leave becomes positively charged