How to Reduce Voltage With Resistors
A resistor is a component that introduces resistance to an electrical circuit. Electrical resistance is a measure of the degree to which a resistor impedes the flow of electricity through the circuit. The standard method of reducing the voltage in a circuit is to add a resistor.
Things You’ll Need:
- Electrical circuit
- Ammeter
- Resistor
- Determine the voltage drop you wish to introduce to your electrical circuit. Assume for this example you wish to reduce the voltage in your circuit by 20 volts.
- Measure the current in your electrical circuit with an ammeter. This generally involves connecting each of the two leads for your ammeter to one of the open ends of the circuit, making the ammeter part of your circuit. Assume for this example that the circuit carries two amperes, or amps, of current.
- Divide the desired voltage drop by the current in the circuit to determine the required resistance of the resistor. This relationship is known as Ohm's law. The voltage must be measured in volts, and the current must be measured in amps to obtain the needed resistance in ohms.
- The voltage drop in this example is 20 volts, and the current is two amps, so the resistor will need to provide a resistance of 20 / 2 = 10 ohms.
- Connect the resistor to the circuit. This generally involves connecting each end of the resistor to a free end of the electrical circuit. The 10-ohm resistor in this example will reduce the voltage of a two-amp current by 20 volts.