electric fields and magnets

• What is an electric field

  • a region where an charged object feels a force
• How do sparks happen in cars

  • fuel from hose can cause a static charge to build up
  • due to potential difference between cars and hose
  • when charge is too big a spark can form igniting the fuel
  • hoses are wired so this doesn't happen as the potential difference between the car and the hose is the same and there's no imbalance of electrons so can't flow
• How is static electricity used in sparys

  • sprays are given a charge
  • making spray droplets repel each other
  • so the droplets spready even
• draw field lines between positive and a negative rod

  there should be 3 equally spaced lines

  
• electric charges

  • more field lines = bigger force
  • point in the direction a positive charge would go so is attracted to positives

  
• What is static electricty

  • static electricity is a build up on charges on insulating materials (materials that don't conduct electricity)
• Why does static electricity not work on conductive materials

  • the electrons flow back leading to no change in charge
• How do objects become electrically charged

  • two objects are rubbed together
  • electrons from one object leave and join to another object
  • the object that's lost electrons become positively charged and the object that's gained electrons has become negatively charged
• With polythene rod and a cloth what happens

  • the cloth rubs it's electrons on the polythene rod causing the rod to become negatibe and the cloth to become postive
• with a acetate rod and a cloth what happens

  • the rod rubs it's electrons on the cloth causing the acetate rod to become positive and the cloth to become negative
• What happens with like and opposite charges

  • electrical objects exert a force on each other
  • like charges repel opposite charges attract but get weaker the further away objects are
• How can you see the charges on two different objects

  • suspend a rod with a known charge on a string ( so it can move)
  • get an object with an unknown charge and put it near the rod
  • if the object has the same charge the rod will move away and if it doesn't the rod will be attracted to it
• Why do balloons stick to the surface of the wall despite the wall having no charge

  • ballons stick to the surface of the wall because when u rub a balloon against ur head electrons are transferred to the balloon making it negatively charged
  • the negatively charged balloon repels the charges on the surface of the wall leaving a positive charge which attracts the balloon
• what is earthing

  • preventing dangerous sparks by connected a charged object to the ground using a conductor
• rules about electric field lines

  go from positive to negative

  closer together = stronger
• How can sparking be explained by electric fields

  • statically charged object will generate an electric field
  • field attracts electrons on other objects causing a flow of charge and leading to sparks
• How does lightning occur

  • raindrops and ice bumb inside storm clouds leading it positively charged white the bottom is negatively charged
  • this creates a huge voltage and a big spark that can damage homes and start fires
• how does static on planes occur

  • friction between air and plane causes plane to become charged
  • build up ofg static charge interferes with communication equipment