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My knowledge of circuits is pretty rudimentary and I've never really understood circuits, so I'm having trouble with the concept of Graetz circuits:

enter image description here

When you register the voltage on the resistor R on a screen of an oscilloscope, you get:

enter image description here

Why is this exactly? As I said, my knowledge of circuits is very limited. My idea:

The sign at the bottom of the circuit means it is an AC current. If the current goes from left to right it will be stopped by the diode above and let through by the diode below (to the left of the resistor) and vice versa if it goes from the right to the left. Is this correct?

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You are absolutely right. –  user17581 Jan 17 '13 at 0:45
    
@user17581 Even with the diodes? I've been confused a lot by this and I've never seen it explained; which way is blocked by the diode; the one in the same direction as the arrow of the diode or the opposite direction? Judging by the looks it could be both but I just assumed the opposite side of the arrow in my answer. –  Ylyk Coitus Jan 17 '13 at 0:49
    
Maybe electronics.stackexchange.com would be a better home? –  Qmechanic Jan 17 '13 at 7:50
    
The way which is blockued is the opposite to the one indicated by arrow in the "arrow against a line" figure that one may imagine looking at the graphical representation of a diode. –  user17581 Jan 17 '13 at 22:38
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up vote 2 down vote accepted

You've correctly deduced how the circuit works. This particular configuration is better known as a bridge rectifier and is often packaged as a single component containing 4 diodes. There are two uses for this - rectifying alternating current as depicted in your question, and creating circuits that can handle direct current with reversed polarity (for instance, in the event a battery is inserted backwards).

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