How to quickly identify the positive and negative terminals of a battery without the use of a multimeter
Usually there are marked on it, if it is hard to see, it is good to have a multimeter to measure it, use DC voltage gear, such as 20 volts or more range, the red pen is connected to one side, the black pen is connected to one side, if it shows a positive voltage, it means that the red pen corresponds to the positive pole, and the other end is the negative pole, if it shows a negative voltage, it's upside down. If you don't have a multimeter, you can also use these pie-in-the-sky methods to judge:
1, from the pole colour to distinguish, the pole is brown for the positive pole, was tile grey for the negative level.
2, generally rely on the battery casing on the front of the label for the positive pole, the reverse is negative.
3, with a wire were connected to the face terminals, immersed in dilute sulfuric acid solution, there are bubbles appearing at the end of the negative pole, no bubbles produced at the end of the positive pole.
4, in the battery poles indirectly a light bulb, constitute a circuit. Put a small magnetic needle under the wire forming the circuit. The direction of the magnetic needle should be perpendicular to the direction of the wire. Use the right hand rule to judge, the direction of the thumb is the direction of current flow. The current flows out from the positive terminal of the battery and flows back to the negative terminal of the battery.
5, the battery poles on the two leads were inserted into the dissected potato, the wire around the green is the positive pole; the other pole is the negative pole.
6, with a high-frequency discharger to detect the comparison of the two batteries, the same reaction has the same polarity. But the trick requires a known polarity of the battery and more professional discharger.
7,The thick end of the column is the + pole (positive), the thin end of the column is the - pole (negative).
8, with the help of salt water to determine the positive and negative battery . Connect a wire at each end of the battery, inserted into the salt water, check the wire threads, producing more bubbles connected to the end of the negative battery, producing fewer bubbles connected to the end of the positive battery. This trick has a little caution, the container of salt water must not be conductive, the general use of porcelain bowl is better. In addition to the commonly used salt water, lye, dilute sulfuric acid, etc., as long as the electrolyte can be used.
9, beaker with copper sulfate solution, closed S, after a few minutes of electricity, if the C carbon rods appear red copper, then A for the positive pole, B for the negative pole; if D carbon rods appear red copper, then A for the negative pole, B for the positive pole.
10, light-emitting diode test method, if the light-emitting diode emits red light, then A is positive, B is negative; if the light-emitting diode does not emit light, then A is negative, B is positive.
