“Inexpensive and functional instruments for the physics laboratory
This time I will show you how to make two simple but very sensitive EMF (Electromagnetic Field ) Detectors. Electromagnetic fields are a combination of invisible electric and magnetic fields of force. They are generated by many devices like power lines, kitchen appliances, mobile phones, computers, but they are also generated by natural phenomena like the Earth’s magnetic field.
Many such projects can be found on the Internet, but most often the only proof of their sensitivity and functionality is the text in the description of the project itself. So I decided to make two devices, one with discrete elements (transistors) and the other with an Integrated Circuit, and test their features that are shown in the video. First, let’s analyze this device made with 4 transistors connected in cascade form. It consists of four NPN transistors, four resistors, and one Led diode. The overall gain is the product of the individual gain of each transistor. The last transistor is connected to a LED diode that signals the presence of static electricity or EMF. In fact, this device is not an EMF detector, but a static electricity detector is known as an Electroscope, specifically this is an Electronic Electroscope. A thin aluminum plate is used as the antenna, and the device is powered by a 9V battery.”