of the Day
Clue of the Month
electrode through which electric current flows into a polarized
Common clues: Battery
terminal; Battery part; Positive pole; Cell terminal; Jumper cable
connection; Battery electrode; + end; Cathode's counterpart;
4 times a year
in English language:
48960 / 86800
anode is an electrode through which electric current flows into a
polarized electrical device. The direction of electric current is,
by convention, opposite to the direction of electron flow. In
other words, the electrons flow from the anode into, for example,
an electrical circuit. Mnemonic: ACID (Anode Current Into Device).
of a zinc anode in a galvanic cell. Note how electrons move out of
the cell, and the conventional current moves into it in the
widespread misconception is that anode polarity is always positive
(+). This is often incorrectly inferred from the correct fact that
in all electrochemical devices negatively charged anions move
towards the anode (hence their name) and positively charged
cations move away from it. In fact anode polarity depends on the
device type, and sometimes even in which mode it operates, as per
the above electric current direction-based universal definition.
Consequently, as can be seen from the following examples, in a
device which consumes power the anode is positive, and in a device
which provides power the anode is negative:
a discharging battery or galvanic cell (diagram at right) the
anode is the negative terminal since that is where the current
flows into the device (see drawing). This inward current is
carried externally by electrons moving outwards, negative charge
moving one way constituting positive current flowing the other
way. It is continued internally by positive ions flowing into the
electrolyte from the anode, i.e., away (surprisingly) from the
more negative electrode and towards the more positive one
(chemical energy is responsible for this "uphill"
a recharging battery, or an electrolytic cell, the anode is the
positive terminal, which receives current from an external
generator. The current through a recharging battery is opposite
to the direction of current during discharge; In other words, the
electrode which was the cathode during battery discharge becomes
the anode while the battery is recharging.
a diode, it is the positive terminal at the tail of the arrow
symbol, where current flows into the device. Note electrode
naming for diodes is always based on the direction of the forward
current (that of the arrow, in which the current flows "most
easily"), even for types such as Zener diodes or solar cells
where the current of interest is the reverse current.
a cathode ray tube, it is the positive terminal where electrons
flow out of the device, i.e., where positive electric current
electrode through which current flows the other way (out of the
device) is termed a cathode.
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