Potentiometer vs Rheostat: What's the difference?

The most significant distinction between a potentiometer and a rheostat is that a potentiometer is used to determine an unknown emf and consequently controls the circuit voltage. On the other hand, a rheostat is a device that regulates the flow of current via a circuit.

The potentiometer compares the unknown emf or voltage to a known voltage to determine its value. By altering the resistance, the rheostat controls the flow of electricity across the circuit. This post will look at the differences between a potentiometer and a rheostat.

Table of Contents

What is Rheostat?

A rheostat is a device that allows you to control the flow of current in an electrical circuit. Increase or decrease the resistance manually to control it. It can adjust the resistance without causing any disruption or stoppage. They’re also used to operate machines like heaters and ovens, which manage heat intensity. However, they are inefficient. They are no longer employed for these purposes as a result of this. Rheostats are now employed in circuits for calibration and tuning.

A rheostat is built similarly to a potentiometer. A rheostat can’t be turned into a potentiometer because it’s only a minor component of a potentiometer. It merely has two connections: one for sliding, such as a wiper, and the other for the resistive element. Rheostats can be divided into three categories. Preset, Rotary, and Linear are all options. Printed circuit boards frequently employ preset rheostats. It is called rotary when the rheostat’s slider or resistive element rotates in a circular motion.

When the slider and resistive element travel straight or linearly, the rheostat is called a linear rheostat. Rheostats are used in various applications, including controlling the loudness of a device like a radio or the speed of a motor. They are also used to dim lights because they can modify lighting intensity. It establishes a serial connection and can control the flow of electricity.

What is a Potentiometer?

In the electronic industry, different types of potentiometers are described using a variety of terminology. Trim pot, sliding pot, and thumb pot are all included. The potentiometer has three terminals, two of which are connected to a resistive element and the other to a wiper. The placement of a wiper determines the output voltage of a potentiometer. It controls the electromotive force of a specific cell and works as a measurement device.

When only two potentiometer terminals are connected, it can be used as a rheostat. A potentiometer’s resistors can offer a fixed amount of resistance, allowing or blocking current flow in the circuit. Ohm’s law, commonly known as Voltage Dividing, can also produce a voltage drop. Two types of potentiometers can be manually adjusted. Linear and Rotary Potentiometers are the two types. When the wiper moves in a straight line, it is linear. When the wiper rotates, it is referred to be rotary.

A potentiometer can be used in a variety of ways. However, the three most common applications are comparing the emf of a standard cell to that of a battery cell, measuring a battery cell’s internal resistance, and measuring the voltage of a circuit in a branch. It is unable to divide voltage. It’s connected in parallel in a circuit. It controls the volume in audio systems and serves as a transducer for television control.

Rheostat vs Potentiometer

Resistors regulate or control signals in mechanical, electronic, and electrical devices, such as the volume of sound, light intensity, and heat temperature.

There are two kinds of resistors:

A potentiometer, sometimes known as a “pot,” is a three-terminal resistor with a sliding contact and an adjustable voltage divider.
A variable resistor with two terminals is known as a rheostat. The rotating rheostat has a curved wire coiled to save space, and the slider or linear rheostat, a straight coiled wire, is the two varieties of rheostats.

Metal ribbons, fluids, and carbon disks are just a few of the materials used in rheostats. It is based on Ohm’s law, which states that as resistance to the current grows, the current will decrease, and as resistance to the current decreases, the current will increase. Because they are not polarized, they can work in the opposite direction.

On the other hand, potentiometers have a resistive element, commonly graphite, that is shaped into an arc and a sliding contact or wiper that goes along the arc. Another sliding contact to another terminal is linked to the wiper. Resistance wire, carbon particles, and cermet can also create it. Potentiometers are available in a wide range of designs and sizes.

A position transducer made with a string is a multi-turn potentiometer. Instead of a dial, the Linear Slider features a sliding control. The resistance between the contact and the terminal is proportional to the distance in a linear taper. Audio amplifiers use a logarithmic circuit with resistive parts that change from one end to the other. The term “digital” refers to something that contains electronic components.

The membrane senses position by contacting a resistor voltage divider with a conductive membrane with a sliding element. Potentiometers are low-power devices that adjust television brightness, contrast, and color and position transducers in joysticks and other systems.

Rheostats are found in various household items, including fans, mixers, power tools, and electric ovens. They’re also utilized to regulate the speed of massive industrial machines’ motors.

Rheostats and potentiometers are still in use today. However, they are being phased out in favor of the triac, also known as the Silicon Controlled Rectifier (SCR), because their mechanical parts rust and deteriorate with time, causing them to malfunction.

Potentiometer Vs. Rheostat: Practical Applications

A potentiometer is used in the power industry to control the speed of DC machines by varying the voltage at the output terminals. It’s also used to control the audio in sound equipment. Frequency matching on ancient radio sets was based on the same concepts as these two arrangements.

To summarize the above explanation, in summary, the following are the results:

The potentiometer and rheostat are two layouts for achieving variable voltage and current levels in electronic circuits and components.

Selecting a Mechanical Potentiometer vs. Rheostat

Even while a potentiometer can be adjusted to perform the same functions as a rheostat, it’s crucial to keep in mind that they have slightly different specifications when choosing these components. Here are some of the most critical requirements:

Maximum Resistance

Keep an eye on the device’s maximum resistance, as this will decide the voltage/current limit given to the load. Typical resistance levels range from tens of Ohms to thousands of Ohms. This should be carefully matched to your power supply and current needs.

Wiper Resistance

In a rheostat, the wiper resistance is critical, and it should be kept to a minimum to ensure that the load receives a correct amount of current. The wiper resistance is unimportant when using a potentiometer to provide voltage to a high impedance load because it is always considerably less than the load resistance. In any event, because the wiper resistance appears in series with the load resistance, you must carefully evaluate how much of a wiper resistance you can accept.

Taper Style

As the wider is moved, the taper shows how the device’s resistance, or rather the resistance division across the slide, changes. When linear functions of the voltage/current provided to the load are required, a linear taper is ideal. An example is a component placed in the feedback loop of an operational amplifier. Logarithmic tapers and an audio taper designed exclusively for audio systems are two other types of tapers.

Power Rating

Potentiometers and rheostats, like conventional resistors, have a power rating. The component may be damaged if the power rating is exceeded.

Tolerance and Hysteresis

Due to the winding architecture and hysteresis, resistance tolerance in potentiometers and rheostats might vary by 10-20 percent in some circumstances. Precision components will have tighter tolerances and more consistent performance (lower hysteresis).

This technique of side-mounting on a PCB is common in volume control applications, and many potentiometers and rheostats support it.

Summery

Carbon disks, fluids, and metal ribbons are among the materials that make up a rheostat. Resistive elements such as cermet graphite, resistance wire, and carbon particles make up a potentiometer.
A rheostat is a device that adjusts the resistance of a circuit. A potentiometer is a device that is used to measure instruments or components.
A rheostat is a device that regulates the flow of electricity. The purpose of a potentiometer is to divide voltage.
In a rheostat, the connection is serial. A parallel connection is utilized in a potentiometer.
A potentiometer cannot be made from a rheostat; potentiometer can be used to make a rheostat.
A rheostat is incapable of dividing voltage. A voltage can be divided using a potentiometer.

Conclusion

While both a rheostat and a potentiometer are devices that monitor two separate properties, such as voltage and current, we can see that they both use the motion of a slider to give significant fluctuation in quantity required for their purpose.

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