The amount by which the voltage drops over across each resistor depends on the relative values of each resistor and the total resistance. The formula for working out the voltage drop across two resistors in series is: One of the most useful ways to use this circuit is to replace R2 with a variable resistor.
If R2 can be controlled by turning a dial then Vout can also be controlled. Another common use of the potential divider is to replace R2 with a sensor such as an LDR. Then as the resistance of the sensor changes, Vout changes as well. This change can then be used to trigger a transistor or can be fed into the input of a microcontroller.
Example: This is a worked example of using the formula above to calculate the missing Vout value for a circuit. Look at the circuit below and take note of the values that are known. Project shopping list For this project you will need the following items, you can adjust the quantities including setting them to zero if you don't need the item , before pressing the "Buy all items" button.
Buy all items. Kitronik's suggested additional learning. How to Calculate Resistors in Series and Parallel. Tags: Electronic principles , Understanding principles. Kitronik Newsletter Sign up now to be the first to know about the latest products and resources! Your email.
If we call this resistor R t , then this is easy to calculate from the fact that it is two resistors in parallel. It is easy to calculate the new value for R t using the formula for two resistors in parallel. In this way it is easy to calculate the effect of any loading by the circuit following the voltage divider. However, the electronic circuit design of the circuits is often chosen so that the voltage divider resistances are much lower, often ten times is a good factor, and in this way the effect of any loading is minimised.
There are very many electronic circuit designs that use a simple voltage divider within them. The examples are too many to include all of them, but a couple of examples are given below:. Volume control in a radio A potential divider using a variable resistor system is the most common way of incorporating a volume control into a radio or other analogue audio system.
Instead of varying the resistance of a resistor, a fixed resistance element is used, and the output point from the resistor is changed as seen in the circuit symbol.
It can be imagined from the circuit symbol, that there is a contact that slides along the resistor element. In this way when the slider is close to the top of the resistive element, a much higher voltage will be seen, but when it moves down the voltage seen will be reduced. In this way the volume of the audio signal can be changed very easily. The electronic components that operate in this way are known as potentiometer, gaining this from the potential divider description.
A typical applications for the potentiometer is within a domestic radio where it enables the volume to be adjusted to the required level. The volume control is normally placed just after the signal has been demodulated and at the input to the audio amplifier. It can be seen that the incoming audio from the demodulator is connected to the top of the potentiometer, and the slider is set to tap off the required proportion of the incoming voltage.
It is set to give the required potential division for the audio level that is needed. Potentiometers come in a variety of formats.
It is important to know how to control the voltages in these circuits to make the applications work! The simplest circuit to start to understand this is the potential divider , which is made up of two resistors in series. Other circuits may be made of more advanced components but often use the same principles of how voltage i.
Sensors can be made from a fixed resistor and a component that has a resistance that depends on whatever is being sensed connected, e. This approach can avoid some difficulties of just using the single element, such as high power consumption. Electrical heaters including room heaters, cookers and hair dryers use a fixed resistance heating element e.
The resistance of the transistor then controls how much voltage is across the heating element and, therefore, how much electrical heating is produced!
This experiment allows you to gain a good understanding of the potential divider. The electrical resistivity of a wire tells us how well the wire material conducts electricity. This is crucial information for any application that involves conducting electricity, including wind turbines, electric vehicles, household electrical goods and computers. Here you can measure the resistivity of wires of different materials and widths, and consider which would be best suited for conducting electricity.
We use materials with low electrical resistivity to transmit electrical power from generators, across grid distribution networks , and to homes and workplaces for use.
Designers of electrical devices rely on knowing the resistivity of wire used in order to calculate the resistance of components. These devices range in size from enormous machines such as wind turbines or industrial lifting equipment ; motors or engines in electric vehicles and all-new electric aircraft ; consumer products such as washing machines, hair dryers and ovens ; and the nanoscale components within the computer chips found in smart devices, laptops, and mobile phones.
Measuring electrical resistivity helps us to understand the properties of materials, to monitor manufacturing processes, and to select the best material for an application. Click on the link below to download the Quick Guide for using the Resistivity experiment. Or follow the brief instructions here:.
Electricity powers the modern world. It is essential for electronic devices, home appliances, travel and school, work and leisure. The widespread use of electricity is because we can make so many components that have different electrical behaviours, and then combine them to make all sorts of devices and machines. These behaviours can be seen most easily by creating a graph of the electrical current I through a component against the potential difference V placed across it.
The simplest component is the electrical resistor. These have fixed electrical resistance , which means the electrical current is proportional to the potential difference and the IV characteristic is linear.
Diodes are made of two different semiconductor materials joined together and only allow electricity to flow in one direcion through them. They are hugely important in electronics and electrical engineering. They are most often used to convert alternating current AC electricity to direct current DC , for example to convert mains electricity into 12 V DC used for charging mobile devices. They are also widely used to protect electronic circuits by preventing unwanted currents.
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