Static electricity

• Protons

  -Protons are positive charges

  -If an object is positively charged, it has less electrons than protons/ it has lost electrons either via induction or friction
• Electrons

  -Electrons are negative charges

  -If an object becomes negatively charged, it has excess electrons
• Neutrons

  -If an object is neutral/has no overall charge, it has equal protons to neutrons
• Which particles dictate charge?

  -Electrons are the only particles that can dictate charge because they are the only particles that can move in and out of the atom
• Charging objects

  -A way to charge objects is through friction, electrons transfer from one material to the other

  -Some materials become positively charged less easily as they hold on to electrons more
• Exam question

  A rod is rubbed with a cloth. After rubbing, the cloth is negative and the rod is positive.

  Explain why.

  -The objects have become charged by friction

  -Electrons transfer the rod to the cloth -The cloth has gained electrons and becomes negatively charged -The rod has lost electrons and becomes positively charged
• Charging by induction


  -When a charged object is brought close to a neutral object, the neutral object can become charged

  -Weather can also affect static electricity
• Uses of static electricity

  -Spray painting

  -Defibrillators

  -Photocopiers
• Spray painting

  -One object being sprayed is connected to a high negative voltage (becomes negatively charged)

  -Spray gun and paint are connected to a high positive voltage (becomes positively charged)
• Why is the spray gun and car body oppositely charged?

  -The spray will be attracted to all areas of the car body, even the hidden areas because opposite charges attract

  -This also results in less paint wastage
• What is the advantage of the paint particles being positively charged?

  -Like charges repel meaning the spray droplets spread out and cover a wider area

  -The spray droplets repel and don't stick together resulting in an even coat of paint
• Dangers of static electricity

  -Earthing is when excess electrons flow either to or from the Earth to balance excess electrostatic charge.

  -When the electrons discharge to or from Earth, a current is caused resulting in a shock
• Lightning


  -Water or ice particles are moved in the clouds by air currents.

  -Friction between the particles cause the bottom of the cloud to become negatively charged and the top to become positively charged

  -When the build up of charge becomes large enough, the negative charge discharges to Earth through the air in the form of a lightning bolt
• Aircraft refuelling


  -A bonding line is used when the plane has just landed and the friction with the air charges the plane

  
• Electrostatic smoke cleaners


  -Smoke is put through a smoke cleaner with a positively-charged metal grid connected to a high positive voltage

  -The smoke rises through the grid and becomes positively-charged

  -These positively charges dust and soot particles attract to the negatively charged plates at the sides

  -Once heavy enough, they will form clumps and these clumps will fall into baskets at the bottom to be taken away

  -After this process, the clean air passes through the chimney free from soot and soot
• Electric fields

  -The space or area around a charge where another charge/object will experience an electric force
• Positive and negative electric fields

  Diagram
• More on electric fields


  -Fields are the strongest where field lines are closer together so in the middle and are weaker away from the middle

  
• Uniform electric fields

  Diagram