Answer to Question #203392 in Electric Circuits for Kara Oregan

Question

You are visiting a friend and you noticed the plastic insulation on the cord to the toaster has a crack and the bare copper wire is exposed your friend gets a shock when making toast what can you tell your friend about what happened what is the specific term for what has happened and what safety feature should/do they have in their home to protect them

Answer 1

While answering this question, I presume that the person who asked this is not from an electrical background, and hence must be wondering why there is a coating over electrical wires.

Electrical current flows when there is a presence of a driving force (called the Electromotive Force or E.M.F.) and a path for current flow. Now, this ElectroMotive Force can be created using a number of ways, for the sake of understanding, let's take the case of electric cells or dry cells.

Here, electrodes (two suitable conducting materials) are kept in the electrolyte (liquid or semi-solid paste-like material). These two chemically react with each other and the result is the accumulation of charged particles at the surface of electrodes. When these charged particles get a way to travel, the negatively charged particles move towards positive ions thus producing what we conventionally call Electric current. This path for electrons is called a conductor (or the wire as mentioned in the question). And we harness the motion of these electrons by placing our equipment (like a light bulb) in between this path. A representational image is shown below.

Now, coming to the question about the coating over the wire. Even without the coating, the electrons will follow in its path so that we can still harness the energy. But it is given for the purpose of the safety of the person nearby or even the pieces of equipment associated with the system.

This is because our Earth is a collection of both positive and negative charges and that too in an enormous quantity but in equal amounts. So we do not feel the effect when we touch the ground. Thus the Earth is said to be at zero potential. Earth can deliver or accept charges without loss of its zero potential (same like addition or removal of some water from ocean will not reduce its level.) But when these charged particles of our electrical circuit explained before, gets any path other than the designated path to reach the ground (or other sources of oppositely charged particles) it will redirect their electrons fully or partially through the other path. The magnitude being dependent on the ease of flow of electrons through the particular material. This property of the material is called conductivity. If this flows through the human body, the result may be fatal. That's when we say a person gets an electric shock. From an equipment point of view, it may drain out the charges of the cell making it useless for the purpose it was made. If we think on a larger scale, the electrical supply system of our locality, state, or even nation may collapse because of faults. To avoid this we use materials to keep the electrons out of the reach of other conductors. This is done by coating the wire with a bad conductor. This bad conducting material is technically called an insulator. The coating you see often on wires is one such insulating material. The insulating material mainly depends on the voltage level (or the E.M.F as stated in this answer) of the system.

Other common insulators used for different purposes in electrical systems are PVC, glass, asbestos, rigid laminate, varnish, resin, paper, Teflon, rubber, etc.

I have tried to explain in the simplest way I knew and I hope this will help to understand insulators better. Suggestions and comments from people who are having electrical knowledge are always welcomed.