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How to Use a Resistor Schematic

A resistor is an electronic device that resists the flow of current in a circuit. In real life, a resistor looks like a small cylinder or tube that has two wires coming out of each end. To read and understand a resistor schematic you need to know how resistors are depicted, be able to calculate the resistance using Ohm's Law and know how to identify resistors connected in series and resistors connected in parallel.

Things You'll Need

Calculator

Instructions

- 1
  Know that a resistor is represented by a zigzag or jagged line on the schematic for a circuit. The resistor's resistance, which is measured in Ohms, is shown as a number next to the jagged line. A variable resistor, a resistor that has more than one resistance value, is represented by a diagonal line going through the symbol for the resistor.
- 2
  Calculate resistance using Ohm's Law. Ohm's Law is V = IR where V equals voltage, I equals current and R equals resistance. Voltage is expressed in volts and current is expressed in Amps. For example, the resistance of a resistor in a circuit with a voltage of 10 Volts and a current of 2 Amps is 5 Ohms.
- 3
  Look for resistors that are connected in series. The total resistance is the sum of the resistors connected in series. For example, two resistors connected in series, one that is 22,000 Ohms and the other 33 Ohms, have a total resistance of 22,033 Ohms.
- 4
  Look for resistors that are connected in parallel by looking for zigzag lines that are on top of each other on the schematic. Calculate the resistance by using the equation R = 1 / ( 1/R1 + 1/R2 + 1/R3 ), where R equals the total resistance, R1 is the first resistor, R2 is the second resistor and R3 is the third resistor.

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