# Problem in understanding bridge rectifier

In a bridge rectifier (full wave) why do the electrons not flow from the other two diodes during a half cycle? Pls help me in understanding the concept.

• Would Electrical Engineering be a better home for this question? Mar 22, 2017 at 18:11
• Include a circuit diagram. Without one, the reader doesn't understand what you're asking. Mar 22, 2017 at 21:19
• @Qmechanic this question needs work. It's low effort and unclear as it refers to "the other two diodes" without any diagram. I think we should hesitate to suggest moving questions to other sites without cleaning them up first, no? Mar 22, 2017 at 21:21
• @DanielSank: Noted. Mar 22, 2017 at 21:37
• Circuit diagram is now there. I agree with @Qmechanic it should be moved.
– toliveira
Mar 23, 2017 at 14:19

Does putting some voltages and voltage-drops across the diodes help?

Note that the diode will only allow current flow when it is forward biased, or else it acts as an opened (unconnected) element.

Your confusion is not uncommon. Students often have a problem with this. My suggestion is to replace the ac input with a dc input which you can swap in polarity. Draw it with the dc battery supply one way round and trace the dc current flow, then do the same with the battery supply the other way round. AC is just DC that "swaps over" regularly. I find most of my students "get it" after this.

• That's how I'm thinking about it, by dividing it into 2 half cycles ( negative and positive) but the problem is still there. In the above diagram follow the blue line from the load (from that negative sign) back to the source. Mar 24, 2017 at 9:07

If the source is an AC source as given in your circuit, the two diodes that are off won't remain off forever. As soon as the source start to be in its negative part of the cycle the ones that are off will turn on and the ones that are on will turn off. Interestingly, the current flowing through the load never changes its direction. That way you will have only positive currents even input voltages are negative.

I know this can get you more confused, but it's worth knowing it. Good luck!!!

In a bridge rectifier (full wave) why do the electrons not flow from the other two diodes during a half cycle? Pls help me in understanding the concept.

First you have to understand the fundamental operation of a diode: it only conducts in one direction.

In a full wave rectifier, there are two diode that conduct when the ac signal goes in a positive direction and the other two diodes are reversed bias. Then when the signal goes negative, the other two diodes conduct while the first pair goes into a reverse bias state (stops conducting).