Transcription
[MUSIC PLAYING]
Welcome back. This lesson is the second in a series about the X-ray circuit. And this lesson is about the secondary circuit.
Remember that the complete X-ray circuit is actually composed of three combined circuits: the primary circuit, the secondary circuit, and the filament circuit. Each of these circuits supports the process of X-ray production in different ways. And this lesson is about the secondary circuit.
So why do we call this the secondary circuit? We call it the secondary circuit because it's on the secondary side of the step-up transformer. Electricity on the primary side of the transformer is in volts. And the step-up transformer converts volts to kilovolts. This makes sense since the X-ray tube is part of the secondary circuit. The X-ray tube uses kilovolts, not volts, to make x-rays.
Transformers work only when using alternating current, but the x-ray tube must operate using only direct current, or DC current. Imagine what would happen if the current was alternating in the x-ray tube. Electrons are supposed to flow from cathode to anode, but an AC current would cause the electrons to flow in both directions. And obviously, that would be a problem.
So how do we fix that? The problem is rectified using rectifiers. Rectifiers convert alternating current, or AC, into direct current, or DC, so that electrons move only in one direction. Notice that the symbol for a rectifier has arrows pointing in only one direction through the circuit. That's because rectifiers cause the current to flow in just one direction.
Here's an example of what that looks like. The alternating current in a transformer has a reversing polarity. This is basically what makes the electrons move in both directions, and that's what makes the transformer work. So in a transformer, that's a good thing, but when the current travels through the rectifiers, it comes out with only one polarity and the electrons travel in only one direction. This is exactly what we want inside of the x-ray tube.
So if you can remember that the transformers use AC and the X-ray tube uses DC, you can remember where the rectifiers are located: between the step-up transformer, which uses AC, and the x-ray tube, which uses DC.
So the secondary circuit contains three major components that we can see in this schematic, and there's a whole lot of converting going on. The secondary side of the step-up transformer is included in this part of the circuit. This works using AC current and converts volts to kilovolts. The secondary circuit also includes rectifiers that convert alternating current into direct current that gets used inside of the x-ray tube. Last of all, the secondary circuit also includes the x-ray tube that receives the kilovoltage in direct current and converts electrons into x-rays.