# Static electricity explained using EMS for SolidWorks

I am sure you would have experienced a static electric shock especially on a dry winter day. You probably know this as static electricity. For some people this is extremely annoying but for some others it could be fun. Maybe you wondered why this happens. In this blog post, I will attempt to explain it using EMS, a multi-purpose simulation package for electro-mechanical applications.

Figure 1 – Static electric shock

You may be thinking that the shock occurs only if you touch a metallic surface like a door knob. Unfortunately, even if you go close enough you could experience a shock. Imagine your finger approaching a door knob on a dry winter day. You have been perhaps walking on a carpeted surface with your rubber soled winter boots. By the time you approach the knob, your body has enough charge because of the constant rubbing between your rubber sole and the carpet. This charge distributes throughout your body especially at the sharp extremities like finger tip. What happens when your finger is at a distance from the knob? And what happens as the distance keeps decreasing?

We have created a small video where we explain what happens to the electric field in the air space between the finger and the metallic knob to explain this phenomenon of a static shock.

As your finger is moved closer to the knob, the charge in your finger creates an electric field. This by itself is no big deal if the strength of the electric field is less than the breakdown voltage of air which is about 3e6 V/m. In the region where the electric field exceeds this value, a breakdown occurs. This means that this region acts like a conductor (yes, air which is normally an insulator can be made a conductor if you produce an electric field greater than the breakdown). As the finger is moved closer to the knob, the breakdown region enlarges and at one point coincides with the conductor (metallic knob). When this happens, the charges from your finger happily moves to the knob creating a current. This leads to a static electric shock.

EMS can help you predict breakdown in your electrical devices. This is highly beneficial for high voltage industry like manufacturers of high voltage insulators, transmission cables etc used in power transmission. By using EMS, you can drastically reduce the need for expensive field testing and there have been instances where customers have even eliminated field testing during product development phase. To get a free full trial of EMS, visit www.emworks.com.