Oct 2020

Static Electricity: Understanding The Laws Of Electrostatics

October 30, 2020

When it comes to static electricity, it is important to get familiar with the laws of electrostatics, electric field, applications, and hazards. Not only is static electricity around us in the devices that we use, but it is essential to know how it happens.

We’re here to help answer any questions about the principles of electrostatics, and ensure that you can learn everything about this key physics topic!

Definition of static electricity

Static electricity is caused by an imbalance of electrical charges on an insulating material. When two insulators touch or are rubbed against each other, it transfers electrons, producing static electricity. Rubbing causes friction, which increases the surface contact and allows for more electrons to be transferred.

It is important to note that the object that loses the electrons will become positively charged, while the object that has gained electrons will become negatively charged, since electrons themselves are negatively charged.

SI unit of charge 

The measurement of electric charges and the quantity of electricity are measured as coulombs (C).

Attraction and repulsion

The key phrase to remember in static electricity is: “Opposite charges attract, while the same charges repel.”

For instance, when two plastic rods have been rubbed with a cloth, they repel each other. This is because as both rods are rubbed with the same type of cloth, they acquire the same charges or electrons. When objects of the same charges come into contact, they repel.

Most objects are neutral as they contain both positive protons and negative electrons, which cancel each other out. However, the number of electrons that are within the objects can be changed through friction or rubbing. This only works with insulators, namely, materials that do not conduct electricity, like cloths. The way in which electrons are transferred depends on the materials that are being used.

Induced charges

Induced charges occur without touching the two objects together. It redistributes the electrons in an object, using a charged object.

One way to see how this works it to first charge one object. You can do this by rubbing a balloon with a cloth. This transfers electrons from the cloth to the balloon, making the balloon negatively charged.

Then, if you bring the balloon close – but not yet touching – to a metal rod, the negative charge of the balloon will cause electrons to migrate away from the balloon. So, this results in the metal rod being more positively charged at the end near the balloon, and more negatively charged at the opposite end.

This process is called induction charging. The total charge of the metal rod has not changed, but distribution of electrons within it has polarised.

Electric field

The electric field is the physical region around an electrically charged particle, in which other charges will be affected by the particle’s electric force. Drawing out electric field lines allow us to visualise the force a charge exerts. These lines show an example of the direction of force exerted on a positive test charge for a positive and negative charge.

Here is the electric field pattern that occurs between 2 particles, during attraction and repulsion:

Applications of static electricity

There are many different applications of electrostatic charges in our daily lives. Here are a few:

  • The photocopier uses electrostatic charges to produce a copy. The image of the page is projected onto a drum that is positively charged. The drum’s coating conducts electricity when light falls on it, and the lit areas of the image lose electrostatic charge. The toner (a negatively charged black powder), is attracted to the positively charged areas and produces a black and white image of the original. The drum rolls against the paper to transfer this image. Then, heat is applied to fix the toner onto the paper.
  • Electrostatic charges is used in painting cars. This is where the paint and car are charged opposite. This allows for the paint on new cars to stick on better.
  • Electrostatic energy is applied in the removal of pollution from smoke-chimneys. There are electrostatic plates placed in the chimneys of factories, which attracts all of the dust and contaminants.

Dangers of static electricity

However, while there are many positive applications of static electricity, it is important to understand the dangers as well. Here are a few that you should note:

  • Lightning is caused by a build-up of naturally-occurring static energy. As you may know, lightning can be fatal to humans, and can also damage trees and property. That is why most buildings have electrical conductors which prevent damages to buildings and people by providing the path of least resistance for the lightning.
  • Sensitive electrical components, such as computer parts, can be damaged by static electricity. One way to prevent any electrical hazards is to handle these parts with wrist straps and place them in anti-static bags. This can help the individual drain off any static charges.
  • Filling fuel on a plane is another hazard as a lot of friction is applied when fuel passes through the hose, making the hose charged. This could lead to a spark or even an explosion. Grounding and earthing are in place for wires that are lined with metal, allowing these charges to be conducted away.

Conclusion

Now that you have a better understanding of static electricity, its key concepts and how it applies in our daily lives, it is vital to continue your physics learning for other topics too! For additional examples, insights and practical uses of static electricity, you should consider enrolling in a physics tuition class today.

With a professional and experienced tutor ready to guide you through any unfamiliar topics or physics concepts during your physics tuition, you’ll be able to learn, improve, and expand your physics knowledge. Sign up today and get started on your physics learning journey!

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