Quite often there is a need to check polarity of a DC power source – the accumulator, the generator or, for example, the rectifier - without the necessary device near at hand.
It is required to you
- - potatoes;
- - bank with water;
- - candle.
Instruction
1. In amateur practice it is possible to arrive as follows. Two bared ends of the wires connected to battery conclusions, lower in bank with warm water in which the tablespoon of table salt is dissolved. Then bring together them until until on the end of one of wires vials of gas – hydrogen begin to appear. This wire will correspond to a negative pole of a source.
2. Cut a tuber of crude potatoes in half, in one of parts from a cut thrust the bared (smoothed-out) wires at distance of 15-20 mm from each other. Near the wire attached to a positive pole of the battery, the surface of potatoes will be painted in green color (oxidation process).
3. The third way. Light a usual household candle. Ship two conductors connected to higher source of tension in a flame of a candle. Under its influence the flame of a candle will become low and wide, and on a wire with a negative charge the thin strip of soot will appear. Besides, it is possible to manufacture the simple indicator for repeated determination of polarity of an unknown source. For this purpose it is necessary to take the usual glass call with the passed electrodes inside (for example, from the fused electrolamp) and closed by traffic jams. In a tubule fill in the solution consisting of one part of saltpeter, 4 parts of the water better distilled or boiled, five parts of glycerin, mix from the one tenth part of phenolphthalein and a part of wine alcohol. It makes sense to use chemical test tubes.
4. The similar indicator can serve very long, at the same time when placing a negative charge there will be a red coloring. If a current source variable, then electrodes give pink coloring. To recheck polarity, will be to stir up the indicator slightly enough.