Conductors, Insulators and Ohm's Law

 Conductors are used in electronic circuits to carry electric currents between various parts of the circuits. Insulators are used when you do not want currents to get conducted between adjacent components in a circuit. The printed circuit board on which electronic components are mounted have both conductors and insulator. The basic material with which the PCB is made is an insulator with very low conductivity of electricity. The circuit printed on it has high conductivity and is usually made of metals like copper. The insulator between plates of a capacitor is known as a dielectric. Sometimes the dielectric is air, which is also a poor conductor of electricity under usual operating voltages. At high voltages, especially if the distance between conductors is less, air can get ionized and act as a conductor, producing arcing. You may have noted this in high voltage overhead lines sometimes.


Current flow through a conductor is measured using an ammeter, which is connected in series. The unit of current is an Ampere. Smaller values can be expressed as milliamperes and microamperes. The symbol 'I' is used for denoting current in a circuit. One ampere can be defined as a charge of one Coulomb passing a given point per second. An ammeter or ampere meter is a modified galvanometer which draws a small portion of the current in a circuit to produce deflection in a moving coil meter. Now we have digital devices to measure current in a multimeter, which can measure many other quantities as well. An electrical current which travels only in one direction is known as a direct current, while a current which alternates its polarity with a definite frequency like 50 Hz of the mains supply, is known as an alternating current.

Ohm's law defines the relation between current, voltage and resistance in circuit, typically for direct current. The current flowing through a circuit is directly proportional to the electromotive force or voltage applied and inversely proportional to the resistance of the circuit. It can be stated mathematically as I = V/R, where I is the current, V the voltage or electromotive force and R the resistance. Voltage is measured in Volts and smaller quantities expressed as millivolts or microvolts. Resistance is measured in Ohms and higher values may be expressed as kilo Ohms and Mega Ohms. The formula of Ohm's law may be transformed to V = IR and R = V/I. So, if two of the values are known, the third one can be calculated.

 

Comments

Post a Comment

Popular posts from this blog

What is LMR SDR?

Image
See also (new post):   Standalone Versions of LMR SDR!  I have been hearing about LMR SDR during discussions among homebrewers for the past few days on 40m. Thought of learning a bit about it and my web searches told me that some of the persons behind the development of LMR SDR are YE3CIF, UT3MK and F5NPV. F5NPV has given detailed descriptions about homebrewing LMR SDR on his webpage, including videos. Even though I did look at the pages of YE3CIF and UT3MK, they seem to be in regional languages. I could not find the expansion of LMR on those pages, though I presume that it would stand for land mobile radio. LMR cables which many of us use were initially designed for land mobile radio. SDR stands for Software Defined Radio like my FT-710, which uses software to do many of the functions done by hardware in the conventional superheterodyne radio receiver . It is interesting to note that LMR SDR covers from 160m to 10m band, that is the whole amateur radio HF bands. There are a few frie
Read more

Building a Tape Measure Yagi for LEO Satellite Operations

Image
 The Moxon Yagi which I have been using for my LEO Satellite operations had a Moxon rectangle for VHF and five UHF Yagi elements which were passively coupled to the VHF Moxon driven element. The gain was not that high when I thought of working SO-121 QRP satellite. VU2TEK had good success with his Tape Measure Yagi which motivated me to go for one. But I don't expect the same success as he was operating outdoors, pointing the Tape Measure Yagi in the direction of the satellite pass. I am planning to use only in a mast mounted fashion which will limit its usability for satellite passes to a short period of about 4 minutes. I have chosen the DK7ZB design which I have been looking at for a quite a long time. That design has 5 elements for VHF and 8 elements for UHF with a boom length of about 1.5m. First step was to get a wooden reaper to use as the boom. Earlier it used to be available in all electrical wiring accessories shops. But now with the usage of PVC channels for wiring, I w
Read more

Six Button Wireless Mouse vs Three Button Mouse

Image
 When I started using computers long back, mouse had only two buttons, a left and a right button. Then came three button mouse with an extra scroll button. I have read that there was also a single button mouse, but I have not seen one. Now here is a six button mouse, that too a wireless mouse with a USB-A Nano Dongle and 2.4 Ghz wireless connection. In the earlier era, mouse had a rolling ball which would gather dirt and sometimes stop functioning well. Now we have optimal mouse which uses a red light source and an optical sensor instead of the rolling ball. The wireless mouse works on a single 1.5 V, AA battery with a projected battery life of one year!
Read more