Why Does Voltage Drop in a Circuit? 2023 Updated

One of the phenomenons in the field of electricity and electronics is voltage. What is it and why should I be concerned about it? In this guide, we are going to look at everything that you should know about voltage drop.

Table of Contents

What is voltage drop?

What is voltage drop? Voltage drop is the reduction in the operating voltage across a conductor. It applies both for resistive load and non-resistive load. An example of resistive load would be incandescent light while an example of non-resistive load would be a fluorescent light.

In an ideal condition, there is no voltage drop as the current flows uniformly through the entire cross-sectional area of the conductor. However, in real-life situations, there will always be some voltage drop due to various reasons.

Causes of voltage drop

There are various factors that are attributed to voltage drop. They include:

1) Resistance of the conductor

2) Contact resistance between two conductors

3) Radiant resistance

4) Increasing length of conductor

5) Environmental effects such as temperature and humidity

Resistance of the conductor

This is the main reason for the voltage drop. The resistance comes from two sources, namely contact resistance and external resistance.

Contact Resistance occurs when two conductors are connected together. It is caused by the imperfect connection of the components such as wire nut or screw terminal.

For example, if you were to solder a wire to a tab of an electronic component, it will take a little bit of time to cool down. This results in the metal being slightly malleable which may cause some level of contact resistance.

The contact resistance is expressed by an empirical value known as the contact resistance factor or CRF. It often ranges from 0.01 to 0.15 ohm depending on how clean it is and the metal used.

External resistance is caused by the surface condition of the conductor such as oxidation and dirt accumulation over time. Oxidation happens when the metal comes in contact with moisture in the air and forms a coating of oxide, which increases resistance to current flow.

Contact Resistance between two conductors

Contact resistance between two conductors is the second major contributor to voltage drop. It is caused by the imperfect connection of the components such as wire nut or screw terminal. For example, if you were to solder a wire to a tab of an electronic component, it will take a little bit of time to cool down.

This results in the metal being slightly malleable which may cause some level of contact resistance. The contact resistance is expressed by an empirical value known as the contact resistance factor or CRF. It often ranges from 0.01 to 0.15 ohm depending on how clean it is and the metal used.

Radiant Resistance

This comes into play when there is a voltage difference between two points. It is caused by energy losses in the form of heat radiation. The losses are due to the fact that resistance creates heat and this heat needs to dissipate. The higher the resistance, the more heat is radiated.

Increasing length of conductor

The longer the conductor, the higher the voltage drop. This is due to two factors, namely the resistance and the capacitance. The resistance increases as the length of the conductor increases while the capacitance decreases. Capacitance is a property of an electric circuit that opposes any change in voltage across it.

Environmental effects such as temperature and humidity

Temperature and humidity are two environmental factors that contribute to voltage drop. Temperature creates resistance in the conductor since electricity travels through metal at a higher speed when it is hot, hence creating more frictional loss. Humidity causes corrosion which increases contact resistance between the metals.

You might be wondering why you should care about voltage drop in your circuit design. Voltage drop can cause a number of problems, including:

1) Diminished power to the load

2) Heating of the wiring

3) premature failure of components

4) Malfunctioning or erratic behavior of equipment

5) Inability to start up a motor

How to minimize voltage drop

There are several ways that you can reduce voltage drop in your circuit:

1) Use higher-quality wiring

2) Minimize the length of the wire

3) Make sure all connections are tight and clean

4) Use a thicker wire gauge

5) Shield cables from environmental factors

6) Use power supplies with low voltage drop characteristics.

How do you calculate voltage drop?

Sometimes it is always necessary to test whether a voltage drop has taken place or not. Maybe you would also like to know the specific margin of voltage drop that has taken place. This information will help you take necessary measures to prevent a further drop. Here are various techniques that you can use to measure the voltage drop.

How to measure voltage drop of a circuit

There are various ways of measuring the voltage drop of a circuit. The easiest way is by using a multimeter. In this method, you will have to do the measurement manually. The process entails connecting the cables and the components involved to a multimeter.

For instance, let’s say you want to measure the voltage drop of a battery pack or even across the resistor in a circuit.

To ensure that you get accurate readings from the multimeter, the red label should always read a higher voltage than the black label.

The first step is to connect the positive terminal of the multimeter to the positive side of the battery pack or resistor or LED. The negative terminal should be connected to the negative side of the battery pack or simply the load.

Record the readings and let’s say it is 6V. This is the average voltage of the new battery packs.

The next step is to determine the voltage across the resistors. The connection is the same as that of the battery pack. Connect the positive lead to the side where the resistor connects to the positive terminal of the battery pack. Connect the negative lead to the negative side of the resistor.

Take note of the voltage reading. Let’s assume you recorded 4.7V

Lastly, let’s find out the voltage across the LED load. To be precise, this is the point at which the LED connects to the resistor. Connect the other side of the multimeter to the negative terminal and record the readings.

From the above connections, it is true that the battery pack supplies 6.4 volts. 4.7 volts are dropped across the resistor and 1.7 across the LED.

The figure below illustrates the voltage drop across the circuit.

Conclusion

I hope that you have learned the essentials of a voltage drop. As we have illustrated, you can easily measure the drop when it occurs and take all the necessary actions to mitigate the situation.

In case you need electronics for measuring voltage drop. Consider involving us. At ICRFQ, we are a reliable supplier and sourcing agent for the electronics in China. Whether you want a multimeter or any other equipment, don’t hesitate to contact us.