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Polarity & Non Polarity Activities

Electronic circuits are made from components that are connected together by conductors such as copper wires. They are powered by sources such as batteries or wall outlets. Electronic components may be polarized, which means that their position in the circuit, relative to the power source, is important. If they are placed facing the wrong way, they may block the flow of electricity and prevent the circuit from working. They may also work incorrectly, or become damaged.

Resistors
- Digital multimeters are used to test and measure electronic components and circuits. They are also able to check polarity. For the first test, use a 1k-ohm resistor. A resistor is a component that can limit the flow of electricity inside of a circuit. Its unit of measurement is the ohm. Turn the multimeter, and switch it to the resistance setting, which is usually indicated by the Greek letter omega. Place the multimeter̵7;s red probe on the resistor̵7;s left lead, and place its black probe on the right. For a resistor with a 20 percent error, the reading will be in the 1200 to 800 ohm range. Switch the multimeter probes. The multimeter reading will remain the same, because a resistor is non-polarized.
Batteries
- Batteries are polarized, as indicated by their plus and minus terminals. To test this, change the multimeter to the DC volt setting, which is normally shown with V or DCV. Take a battery and put the multimeter̵7;s red probe on its plus side and the black probe on its minus side. The display will show a positive voltage. Switch the probes and the display will show a negative voltage. For example, a 9V battery will first show 9 volts. It will show ̵1;9 volts when the probes are switched.
Diodes
- Diodes are semiconductors that limit the current flow in a circuit to one direction. Like batteries, they are polarized. Their negative side is marked by a stripe. One way to check a diode̵7;s polarity is to measure its resistance. Another method is to use the multimeter̵7;s diode setting. The setting is normally marked by a diode symbol, which looks like an arrow with a vertical line at the front. Place the red probe on the diode̵7;s positive lead and the black probe on the negative lead. The multimeter will show a voltage reading around 0.7 for a silicon diode, for example. Switch the probes and the reading will show that the diode is non-conducting.
LED Circuit
- LEDs are diodes built to emit light. To demonstrate their polarity, build a series circuit with a 1k-ohm resistor and an LED. Insert the resistor into a breadboard, making sure that each of its leads are in different columns. Use a jumper wire and connect the resistor̵7;s right lead to the breadboard row designated as the positive voltage source. Place the LED̵7;s positive lead, which is the longer leg, into the same column that the resistor̵7;s right lead is in. Put the LED̵7;s left lead into a different column and use a jumper wire to connect this column to the row on the breadboard that is designated as ground. Put two AA batteries or a 9V battery into a battery holder. Attach the holder̵7;s red lead to the breadboard̵7;s positive voltage row, and its black lead into the ground row. The LED will light. Remove the resistor, turn it around, and place it back into the circuit. The circuit will not change. Turn the LED around, and it will no longer light.

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