In electrochemistry, follow the usage habits of physics. In the primary battery, the device is the power supply, and the electrode with high potential flowing out of the current is the positive electrode, which plays a reducing role, that is, ions or molecules get electrons; In the electrolytic cell, the device is an electrical appliance, and the electrode connected to the anode of the power supply plays an oxidation role, that is, ions or molecules lose electrons, which is different from the primary battery. Negative pole with symbol+:one pole where electrons are lost, oxidation reaction occurs and electrons in the external circuit flow out.
External circuit: electrons flow from negative electrode to positive electrode; Current flows from the positive electrode to the negative electrode.
Directional motion of anions and cations in the internal circuit: anions move to the negative electrode and cations move to the positive electrode.
The difference between positive electrode and negative electrode
Determination of anode and cathode of primary battery
Judging from the electrode reaction
From the point of view of electrode materials
2. Current direction of internal and external circuits and movement direction of conductive particles
3. General conditions for forming a simple primary battery
Using two conductors with different activities as electrodes, the two electrodes are kept in contact and inserted into the electrolyte solution (loop). The overall reaction is a spontaneous (energy-releasing) redox reaction. [2]
Distinguishing between positive and negative poles of storage battery
Method 1:
When the "+"and "-"marks are blurred, the battery electrode painted in red represents the positive electrode, and the electrode painted in blue is the negative electrode. If the battery is used for a long time, the color may become dark. Generally speaking, however, a battery positive electrode with a slightly thicker pole column and a battery negative electrode with a slightly thinner pole column.
Method 2:
Judging the positive and negative poles of the battery by DC voltmeter. Connect the battery to the DC voltmeter. When the voltmeter pointer indicates normal, the battery anode is connected to the voltmeter anode, and the battery cathode is connected to the voltmeter cathode.
Method 3:
The anode and cathode of unknown polarity battery are judged by high frequency discharger and battery with polarity mark. The two batteries were tested and compared by high frequency discharger, and the polarity of the same end was the same. However, this move requires a battery with known polarity and a more professional discharger.
Method 4:
Judging the positive and negative poles of the battery with the help of brine. Connect a wire at both ends of the battery, insert it into salt water and check the end of the wire. One end with more bubbles is connected to the negative electrode of the battery, and the other end with less bubbles is connected to the positive electrode of the battery. This move is a little cautious. Containers of salt water must not conduct electricity, and porcelain bowls are generally better. In addition to ordinary salt solutions, alkaline solutions and dilute sulfuric acid can also be used as long as they can form electrolyte.
Method 5:
A light bulb is indirectly connected between the two poles of the battery to form a loop. Put a small magnetic needle under the wire that forms the coil. At this time, the direction pointed by the magnetic needle should be perpendicular to the direction of the wire. Judging from the right-hand rule, the direction pointed by the thumb is the direction of current flow. The current flows from the positive battery and returns to the negative battery.