GCSE Physics: Static Electricity and Electric Fields

Static electricity and electric fields are part of the electricity topic in separate (triple) GCSE Physics, for example in AQA's specification, and they are not in combined science. This material covers the whole of that content with an emphasis on explaining everyday observations.

It starts with how objects become charged. When two insulating materials are rubbed together, electrons are transferred from one to the other by friction; protons do not move. The material that gains electrons becomes negatively charged and the one that loses them becomes positively charged by the same amount, so a polythene rod rubbed with a cloth becomes negative while an acetate rod becomes positive. You explain why a metal rod held in the hand cannot be charged this way: it is a conductor, so charge flows away through your body to earth.

Next come the forces between charges. Like charges repel and unlike charges attract, and the force acts without the objects touching. You predict what a hanging charged rod does when another charged rod is brought near it, and you explain why a charged balloon sticks to a neutral wall and why a thin stream of water bends towards a charged rod: the charged object induces an opposite charge on the nearest surface, which is then attracted.

Sparking and safety follow. When the potential difference between a charged object and earth becomes large enough, electrons jump across the gap as a spark, which is why you can get a shock after walking across a nylon carpet. Charge building up during refuelling could ignite fuel vapour, so aircraft and tankers are connected to earth by a conducting cable.

Finally you use the idea of an electric field. A charged object is surrounded by a field that is strongest close to it and weaker further away; another charged object in the field feels a force that grows as the distance shrinks. Around an isolated charged sphere the field lines are radial, pointing away from a positive sphere and towards a negative one. The field explains both the non-contact force and sparking, when the field is strong enough to ionise the air.

The material offers three formats. The quiz has 12 questions mixing single-answer and multiple-answer items, each with an explanation. The flashcards give quick revision of key facts and definitions. The written work is a printable sheet of 8 longer explanation questions of the kind set for six marks, which you answer by hand and upload for feedback on each answer.

• Explain charging by friction in terms of electron transfer
• Predict and explain the forces between charged objects, including induced charge on neutral objects
• Explain why conductors are not easily charged by rubbing and how earthing works
• Explain sparking and the use of earthing for safety when refuelling
• Describe the electric field around a charged sphere and how field strength and force change with distance

Practice material written by Zestly, based on the DfE GCSE physics subject content (static electricity and electric fields, physics only), with AQA GCSE Physics 8463 section 4.2.5 used as the example specification.