Capacitance

 
Capacitance

What is capacitance? Electric capacitance is the ability of a conducting body to accumulate charge. The capacitance value of a capacitor is obtained by using the formula: where C is the capacitance, Q is the amount of charge stored on each electrode, and V is the voltage between the two electrodes. In real life circuits the amount of charge on one plate equals the amount of charge on the other plate of a capacitor, but these two charges are of different signs. By examining this formula it can be deduced that a 1 F capacitor holds 1 C of charge when a voltage of 1V is applied across its two terminals. The unit of capacitance The unit of capacitance is a Farad [F]. This unit can be somewhat impractical. From the vantage point of most electrical engineers, one farad is a huge capacitance value. Most electronic circuits use capacitors of only up to a few mF. There are several good reasons for this. One reason is that, when dealing with signals in an electrical circuit, as the frequency of the signal increases, the need for high capacitance capacitors decreases because, at higher frequencies, even a small capacitor can make a big impact on the circuit. Since most modern digital circuitry has a tendency to move towards higher frequencies in order to meet demands for improved processing speed, these circuits mostly use capacitors of only up to a few mF. As a result, the need for large capacitors is virtually non-existent in the signals processing parts of electrical circuits. Another reason is that high capacitance capacitors are physically large. Therefore, the use of such capacitors is avoided, especially in mobile devices. However, there have been recent technology advances in the field of supercapacitors. Thanks to these advances, it is now possible [… read more]

Electric Field

 
Electric Field

What is an electric field? An electric field is a special state that exists in the space surrounding an electrically charged particle. This special state affects all charged particles placed in the electric field. The true nature of electric fields, as well as the true nature of an electric charge is still unknown to scientists, but the effects of an electric field can be measured and predicted using known equations.  Just like a magnet creates an invisible magnetic field around it, which can be detected by placing a second magnet in its field and measuring the attractive or repulsive force acting on the magnets, electric charges create an electric field which can be detected by using a test charge. When a test charge is placed inside an electric field, an attractive or repulsive force acts upon it. This force is called the Coulomb force. In fact, magnetic and electric fields are not entirely separate phenomena. A magnetic field that changes with time creates – or “induces” an electric field, while a moving electric field induces a magnetic field as a direct consequence of the movement. Because these two fields are so tightly connected, the magnetic and electric fields are combined into one, unified, electromagnetic field. Electric field definition The electric field can be defined as a vector field which describes the relationship between the charge of a test particle introduced in the field and the force exerted upon this charged test particle.  Where E is the electric field, F is the force exerted on the test particle introduced into the field and q is the charge of the test particle. The unit for electric field is volts per meter [V·m-1] or newtons per coulomb [N·C-1]. The application of electric field in capacitors Electromagnetism is a science which studies static and [… read more]