Magnets, electromagnets, sources of constant tension and devices with unilateral conductivity have two poles. In the first cases these poles are called northern and southern, and in the second - negative and positive.
Instruction
1. For definition of poles of a magnet take the second magnet on which poles are designated by letters (N - northern, S - southern) or flowers (red - northern, green, blue or gray - southern). The North Pole of a test magnet will be attracted to southern the examinee and vice versa. Test and test magnets have to be approximately identical force, otherwise magnetic reversal of that from them which is weaker is possible. At the address with strong magnets be careful not to get a mechanical injury of fingers.
2. For determination of polarity of a vypryamitelny element with unilateral conductivity connect to it an ohmmeter in one in the beginning, and then in other polarity. The element at the same time has to be deenergized. If the probe at which there is negative tension is connected to the cathode, and the probe with positive tension - to the anode, the device will show resistance much less infinity. At analog devices the polarity of tension in the mode of an ohmmeter is usually opposite to polarity of tension which should be put to the same probes in the voltmeter mode. At digital devices these polarity most often coincide. At emergence of doubts check the device on the diode which arrangement of conclusions is known.
3. To define poles of a source of constant tension, connect to it the voltmeter on which the corresponding limit is previously exposed. If the source develops voltage over 24 V, follow at the same time safety rules. Probes of the voltmeter have the next colors: black or blue - minus, white or red - plus. At the analog voltmeter at the wrong polarity of the shooter will deviate slightly to the left and will rest against the limiter, and at digital - on the indicator before number the minus will appear. Consider that at incorrectly chosen limit force applied to an arrow can be so big that the last will be bent.
4. Define poles of an electromagnet in the same way as magnet poles. When changing polarity of its supply voltage they will trade places. If the winding of an electromagnet is reeled up clockwise, to a negative conclusion there will correspond the North Pole, and positive - southern. At an electromagnet which winding is reeled up counterclockwise, compliance of conclusions to poles opposite. Even if the winding eats low voltage, be careful of the impulses of a self-induction arising at the moments of interruption of current.