Or from another usually reliable source: For example, in an electron tube electrons from the cathode travel across the tube toward the anode, and in an electroplating cell negative ions are deposited at the anode. In a battery or other source of direct current the anode is the negative terminal, but in a passive load it is the positive terminal. Compare anode.Īnode, the terminal or electrode from which electrons leave a system. Within a gas discharge tube, electrons travel away from the cathode, but positive ions (current carriers) travel toward the cathode.
This terminal corresponds in electrochemistry to the terminal at which reduction occurs. How about from the Encyclopedia Britannica, a generally reliable source: Ĭathode, negative terminal or electrode through which electrons enter a direct current load, such as an electrolytic cell or an electron tube, and the positive terminal of a battery or other source of electrical energy through which they return. Those definitions aren't so hard, it's just that we are so used to things like vacuum tubes and diodes being biased Anode positive and Cathode negative that we forget/ignore the definitions (or maybe never learned them), and we automatically extend the labelling to sources where it doesn't quite work. Electrochemically, that is the terminal at which reduction takes place.
If Electrons are entering, that terminal is the Cathode. Those are the definitions of Anode and Cathode. An Anode of a device is the terminal thru which Electrons leave the device.A Cathode of a device is the terminal thru which Electrons enter the device.(It is often a matter of developing confidence.) But that is all about developing a mature attitude to learning and figuring things out for yourself before just asking questions. It is essential to look at a number of sources for this sort of information because there are always sources that are just plain wrong. When someone claims to be "confused" by a name, it is really up to them to take it on themselves to accept it rather than to look for a reason that the name is 'wrong'. If a device can work when connected up in different ways then that's another level of understanding and a better nomenclature may be called for. The name that is given to something is supposed to help people to have an idea how it will behave. It would be futile to say that, when a diode has broken down with excess reverse voltage, the Cathode has suddenly become the Anode. What is called the Anode of a diode is the terminal that is positive when the diode is 'forward conducting'. PF is always getting questions about the Names of things and the confusion that results from insisting that the Name is more important than the Function of an item. However we are used to an Anode being the more Positive electrode for most of the components we use. The Anode is where the Oxidation reaction occurs (the reaction that frees up Electrons). This seems to be an endless source of confusion. Also, I can't think of the anode as being positively or negatively charged since it changes depending on if the battery is charging or discharging. For electron flow, the anode is where electrons flow out of, and the cathode is where the electrons flow into. For conventional current, the cathode is where current flows out of and the anode is where current flows into. Thanks so much for your help, but let me try to summarize my understanding now. Remember that electron flow is in the opposite direction from current flow. Yes, from out of the device, not into the device. Current will flow through the diode when the anode is more positive than the cathode, ie same as an LED working properly, and emitting light. One can see that, the cathode is where the CURRENT comes out of the device.įor an LED to work and emit light, one wants the current to come out of cathode, which is the pointy end in the figure.įor a regular diode, the pointy end is labeled the positive terminal in a general circuit diagram, but if biased in such a manner, no current flows through the diode device. For an element in a circuit, the anode/ cathode can change, such as for a battery discharging or charging.įor discharge, the positive terminal is the cathode.įor charging a battery, the positive terminal becomes the anode.
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