Skip to main content

ELI the ICE man

In a previous lesson, we covered the fact that two alternating currents can be either in phase, or out of phase with respect to each other. We also discussed the addition of two sine waves of differing phase by using VECTOR ADDITION. I am fairly certain that you were hoping you would never see this again. Sorry, but you were SO wrong. We are soon going to get into the practical applications of vector addition. You are about to learn that in electronics, the capacitor and the inductor are exact opposites. The reason for this is because they BOTH store electricity, but in different ways. In a purely resistive circuit, there is no change in the phase from one component to another. When we add an inductor or capacitor into the circuit, however, the game changes completely, and the rules to the game are written with vectoral math.

Note that if we were to find the resistance of a series circuit with 2 resistors, one having 3 ohms, and the other having 4 ohms, we would simply add them, and come up with 7 ohms. If we were to graph this, we would have a single line along the "X" coordinate which is 7 units long, with points at 0, 3, and 7. If, however, we were to plot the Combined Resistance of a coil ( remember XL ? ) and a resistor we would have to plot a graph like the one above and to the left. This combined resistance is called IMPEDANCE, which is the TOTAL RESISTANCE TO THE FLOW of current. Note that Impedance is the TOTAL resistance to the flow, which includes "pure resistance" (from resistors), capacitive reactance, inductive reactance. The symbol for impedance is Z.

If you have ever studied trigenometry, or even basic geometry, you may recall the formula for finding the hypotenuse of a right triangle ( A2+B2=C2). This will come in handy, as you compare it to the formula for impedance:
This can be re-written as
Now let's assume that we have a series circuit like the one shown on the left. Using the formula for IMPEDANCE ( Z ), R2 would be 32 which equals 9. XL2 would be 42 which would be 16. 9+16=25. The square root of 25 = 5, so the impedance of the circuit would be Z=5. Sometimes we might say that the "complex representation" of Z = R+Xj. In this case it would be 3+4j. This comes in handy as we begin adding capacitors into the circuit. Capacitors are like the opposite of inductors in a circuit. Whereas inductors are added ( Z = R + Xj ).... capacitors are subtracted (Z = R - Xj ). I know this all sounds confusing, but it will become clear as mud shortly.

Recall the formula for Inductive Reactance?
XL = 2πfL

How could you forget? Well, CAPACITIVE REACTANCE is its opposite, and should also be memorized. Ready for this one?

XC = ----------------

WOW! It's almost the same formula! The only difference is that we substituted the L's for C's, and we reciprocated the formula (divided 1 by the formula). In the great scheme of things, that makes this formula not too difficult to remember, assuming you did memorize the formula for inductive reactance when I told you to. If you didn't, take time now to memorize both formulas. Your survival in electronics depends on them. Notice that I have flashed lots of formulas by you, but I have only asked you to memorize 3 of them... Ohm's Law, and the formula's for inductive and capacitive reactance. That is because you will use them over, and over again.

Now let us examine our capacitive circuit. Once again, it has a resistance of 3, and a reactance of 4, but this time, it is a capacitive reactance, and not an inductive reactance. We will again use the formula for IMPEDANCE ( Z ), R2 would be 32 which equals 9. XC2 would be 42 which would still be 16. 9+16=25. The square root of 25 = 5, so the impedance of the circuit would once again be Z=5.

    But there is a catch - this time, because the circuit is CAPACITIVE, we would have a complex representation of impedance being equal to 3 - 4j. What exactly does this mean? It means that instead of plotting our graph in the POSITIVE direction along the Y axis of our graph, we would plot it in the NEGATIVE direction. Instead of our plotted point being (3,4) it would be located at (3,-4). I realize, of course, this is a lot of math to remember, but unless you are designing radio frequency, or other resonant circuits, you probably won't be using these formulas on a daily basis. You should be familiar with them though, and you SHOULD memorize the formulas I have pointed out thus far.
One important point to keep in mind, is that when current flows through a purely resistive circuit, the voltage and current arrive at the same point at the same time. In other words, Voltage and Current are in phase in a purely resistive circuit. In a circuit which contains inductance or capacitance though this is not so. In an inductive circuit, the voltage leads the current by 90 degrees (assuming a purely inductive circuit). Likewise, in a capacitive circuit, the current leads the voltage by 90 degrees. Which leads which is easy to remember. Just think "Eli the Ice man".
    E=Voltage I=Current... L=Inductor......C=Capacitor
  • ELI Inductive circuit...... Voltage arrives before Current .
  • ICE Capacitive circuit... Current arrives before Voltage.

Popular posts from this blog

Build a Low Noise And Drift Composite Amp Circuit Diagram

How to Build a Low Noise And Drift Composite Amp Circuit Diagram. This circuit offers the best of both worlds. It can be combined with a low input offset voltage and drift without degrading the overall system`s dynamic performance. 
 Low Noise And Drift Composite Amp Circuit Diagram

Compared to a standalone FET input operational amplifier, the composite amplifier circuit exhibits a 20-fold improvement in voltage offset and drift. In this circuit arrangement, A1 is a highspeed FET input op amp with a closed-loop gain of 100 (the source impedance was arbitrarily chosen to be 100 kfl). A2 is a Super Beta bipolar input op amp. It has good dc characteristics, biFET-level input bias current, and low noise. A2 monitors the voltage at the input of A1 and injects current to Al`s null pins. This forces A1 to have the input properties of a bipolar amplifier while maintaining its bandwidth and low-input-bias-current noise.

High Power Output Amplifier TDA7294

The famous SGS-THOMSON ST Microelectronics has introduced a Hi-Fi DMOS high-power amplifier circuit TDA7294, its sound great taste bile, which due to its internal circuit from input to output are field-effect devices, rounded sound Mild, delicate Rounuan.  However, with its assembly amplifier, only TDA7294 single-output power is only 70 W, BTL access law is 100 W from top to bottom, do not feel that power cushion. The author several tests, used to promote TDA7294-level, direct-drive one to four pairs of high-power transistor parallel, the output of strong currents, the power output of 400 W (mono), and the circuit is simple and no need to debug that can reliably work Basically, the IC has maintained a sound and performance.  Ruzuo The figure below shows, R6 for the feedback resistor, the author of the value in debugging 22 k Ω more appropriate, R6 also decided this circuit gain, the gain value will increase.  Quiescent current depends on the power of R7, R8, when its value…

Full Power Mobile Phone Jammer Circuit Diagram

Full Power Mobile Phone Jammer Circuit Diagram.To day if we are talking about expert Cell phone Jammers we are conversing about this schematic underneath. First off all you should be very very cautious how to use this apparatus. Its completely illegal and so the reason. I post this Circuit is only for educational and testing causes. This type of apparatus is being utilised by security for VIPS, particularly at their limousines to avoid blasting device initiating while the vehicle passes from the goal cell phone-bomb. Off course there are those who use it to make a antic or to make the persons crazy in the rectangle block you are. 
The power of the jammer is currently sufficient to do your thing, but certainly you can place a 30W linear power amp at the RF output and impede a much wider locality. So, Be pleasant individual with that and recall that there are people who may need desperately to obtain or make a call and one of them could be you! And if you can't oppose of functioning …