Skip to main content

Ohm's Law

Thus far, we have discussed current, resistance, and voltage. Now we shall discuss the important relationship that exists between the three. Around 1840, German physicist Georg Ohm noted that there was a distinct mathematical relationship between Voltage, current and resistance. He then wrote the basis for what we now call OHMS LAW . Ohm's Law states that Voltage (in Volts) is equal to the product of the current flowing through a resistance within a circuit. In other words... Voltage = Current times Resistance.

Now comes the bone in the throat of the student. While we measure Voltage in Volts, we often use the letter E to represent Voltage. This is because another word for Voltage is ELECTROMOTIVE FORCE, which is shortened to EMF or simply E. Also, we use the letter I to represent current. So that our formula becomes:

So what does this mean? Simply put, if we have a resistance of 10 Ohms (R=10), and a current of 10 Amps(I=10), we will have a Voltage of 100 Volts, because 10*10=100 (E=100).

Ohms law can also be stated two other ways. By using basic algebra, we can turn the formula around to make it say:


Learning about Ohm's Law is fine and dandy, but if you are going to USE Ohm's law on a regular basis, you really ought to memorize it. Memorizing Ohm's law may sound like a time consuming and daunting task, but if you do it the Electronics Theory.Com way - you'll have it committed to memory for life within a few minutes!

You just have to imprint a picture in your mind. Years ago, Native American Indians used to roam the plains of the United States. These Indians would look across the plains, and see all kinds of animals. They would see rabbits running across the field, and eagles soaring in the sky. Now, picture things from the Indian's stand point - he sees the Eagle flying over the Rabbit:

Say to yourself Indian equals Eagle over Rabbit.

Now just use the first letter of each word: I = E over R, which is this formula:

However, from the Rabbit's point of view, he sees things a little differently. The Rabbit looks out and sees the Eagle flying over the Indian.

Say to yourself Rabbit equals Eagle over Indian.
Now just use the first letter of each word: R = E over I, which is this formula:

Finally, the Eagle up in the sky sees both the Indian and the Rabbit standing on the ground together.

Say to yourself Eagle equals Indian and Rabbit together.
Now just use the first letter of each word: E = IR, which is this formula:

Now if you simply remember the story of the Indian, Eagle and Rabbit, you will have memorized all three formulae.


But of what significance is it? Here is the gist of it. If we know 2 out of the 3 factors of the equation, we can figure out the third. Let's say we know we have a 3 Volt battery. We also know we are going to put a 100 W resistor in circuit with it. How much current can we expect will flow through the circuit?

Without Ohm's Law, we would be at a loss. But because we have Ohm's Law, we can calculate the unknown current, based upon the Voltage and Resistance.

Let's try another problem. Say we have the circuit below. We know the Voltage and the Current, because we have meters to indicate such in the circuit. When we plug in the unknown load resistance, the Voltmeter reads 45V and the Ammeter reads 2 Amperes. What is the resistance of the load? IT IS A PICTURE OF WHAT'S DESCRIBED IN THE TEXT. DOWNLOAD A BROWSER THAT SHOWS PICTURES!

Well now, if'n I done my math a'right, I should be using this formula:

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 …