Types of Resistors : Resistance, Power, Uses, and Details

Types of resistors need to be studied and remembered seriously. This topic is crucial when designing and building an electrical circuit. Every resistor has different resistance, tolerance, and power rating. This guide is made to explain the types of resistors in a simplest way. Even the resistors can be divided into many categories, there are no “types of resistance”.

Resistor is an electronic component used to resist flowing current in the electrical circuit. As the name implies, it has a resistive characteristic and one of the passive elements. Resistor is measured in Ohm (Ω). Just as we get from Ohm’s law, the resistance is inversely proportional with the flowing current. Resistors have values we need to pay attention:

• Resistance
• Tolerance
• Power rating

You will find all of these values when using a resistor to build a circuit. Don’t worry, the factory that produces the resistor will list its specification on the packaging.

Types of Resistors

For the basic knowledge, we can divide the types of resistors into two main groups: linear resistor and non-linear resistor.

Linear resistor

This type of resistor has a linear voltage-current relationship curve, hence it fulfills the Ohm’s law theory. Linear resistor is divided again into:

• Fixed resistor
  This type of resistor has a fixed value of resistance and we can’t change it in any way. There are examples for fixed resistor:

• 1. Wirewound resistor
  2. Carbon film resistor
  3. Metal film resistor
  4. Metal oxide resistor
  5. Metal strip resistor
  6. Zero-ohm link
  7. S I P resistor network

• Variable resistor
  This type of resistor has a variable value of resistance depending on how we treat its “controller”. Some of them have rotary or sliding parts. Linear variable resistor we can find are:

• 1. Potentiometer
  2. Trimmer
  3. Rheostat

Non-linear resistor

This type of resistor doesn’t follow Ohm’s law because its voltage-current relationship curve is not linear. Unlike the linear resistor, the non-linear resistor has its resistance affected by external factors such as temperature and light intensity. These resistors can also be put in variable resistors. Non-linear resistors we can find is:

• Thermistor
• Light Dependent Resistor (LDR)
• Varistor

Type of resistors can be divided into their materials and resistances.

Types of Resistors : Material

Depending on the material used to make a resistor, we can make the types of resistors listed below. Don’t worry, we also put the resistor type images.

1. Wirewound resistor

Wirewound resistor is made from a manganin or constantan wire, wound around an insulating material shaped in a cylinder. Wirewound resistors are high power resistors.

Wirewound resistor is a type of resistor which is very compatible for a circuit that needs high precision, smaller tolerance, and very low temperature coefficients. With different lengths and diameter of the wire, we can get various resistance and power ratings.

Besides these characteristics, wirewound resistors have advantages such as:

• High power rating.
• Temperature coefficient almost zero (resistance value won’t be affected by temperature change).
• Wounded wire is covered by a high heat resistance such as baked enamel (resist the resistance variation by temperature changes).
• Small resistance tolerance (± 0.01% to ± 1%)
• High power rating (5 – 200 W)

Besides these characteristics, wirewound resistors have disadvantages such as:

• We better avoid this resistor when dealing with high frequency application because this resistor is made from wrapped wire around an insulated core, in other word is an inductor by nature.
• High cost

2. Carbon film resistor

This is also known as a carbon composition resistor. This type of resistor is widely replaced by the metal type resistor for wide applications because of its worse tolerance and noise. Even if they get replaced, it is still common to use this type as a simple circuit and learning.

This resistor is made from carbon film formed into ceramic substrate. This carbon film has its own advantages such as:

• Almost always available
• Low cost
• Durable
• Excellent insulator
• Non-inductive
• Has a large cross-section.

Since it has low inductance, it will be useful when dealing with high-frequency applications. Because it has a large cross-section, it has a higher power rating and survivability.

This carbon film has its own disadvantages such as:

• Very sensitive to temperature change
• Wide tolerance range (± 5% to ± 20%)
• Produce electric noise

This type of resistor is made from carbon. This resistor is very common in practical fields and transactions. The power rating varies from

• ⅛ (0.125) W
• ¼ (0.25) W
• ½ (0.5) W
• 1 Watt
• 2 Watts

3. Metal film resistor

This metal film resistor as the name implies uses metal film. This metal (ruthenium) is placed into an insulating substrate. Its size is smaller and more available to mass-produce.

In most applications, this type of resistor replaces the carbon film resistor because it has better temperature coefficients, lower noise, tighter tolerance, and better precision.

4. Metal oxide resistor

This resistor is similar to metal film resistor but its resistive element is an oxide such as tin. Metal oxide resistors are better for higher power rating circuits than metal film resistors.

Metal oxide resistor is made from a ceramic core coated with a thin film of metal oxide such as tin oxide. Its tolerance is 1% or 2%. Its shape and size is similar to a carbon resistor but with different color bands and number of bands. Its power rating is similar to carbon resistor as:

• ⅛ (0.125) W
• ¼ (0.25) W
• ½ (0.5) W
• 1 Watt
• 2 Watts

5. Metal strip resistor

This is a special resistor for the current measurement instrument in a power supply. As the name implies, this resistor is a laser-trimmed metal strip with low thermal resistance and able to carry high current.

Read also : difference BJT vs MOSFET

Types of Resistors : Resistance

Depending on resistance values, we can divide resistor into:

Fixed resistor

Fixed resistor is made with fixed resistance and can’t be changed. This resistor is commonly used for electronic circuits as current limiter. We can find this type of this resistor on:

• Wirewound resistor
• Carbon film resistor
• Metal film resistor
• Metal oxide resistor
• Zero-ohm link
• S I P Resistor Network

Resistor network

Resistors with the same value are packed together as an “item” just in case we need multiple resistors with the same resistances. This resistor pack is sold as single inline (SIL) and dual inline (DIL). It can be either non-connected or connected resistors.

Variable resistors

Variable resistor is a resistor with variable resistance depending on what controls it. The most common examples of this types of resistors is:

• Varistor
  This resistor does not obey Ohm’s law since it has a non-linear voltage-current relationship curve.

• Potentiometer
  We can adjust the resistance of this type of resistor directly. We can use its rotary part to adjust the resistance.

• Trimmer potentiometer
  This resistor is similar to potentiometer but the rotary part is replaced with a small part to rotate. Sometimes we need to use a screwdriver.

• Rheostat
  This one is similar to a potentiometer but it only has two terminals. It is widely used for current controllers.

• Thermistor
  Thermistor comes from “thermal resistor”. The resistance of this resistor depends on the temperature around the thermistor. Thermistor has a negative temperature coefficient. This means the resistance falls down as the temperature rises. This is mainly used for simple temperature sensors combined with ADC and voltage source.

• Light Dependent Resistor (LDR)
  The resistance of this resistor depends on the light intensity received by the LDR.

Types of Resistors : Function

Resistor can be divided according to its function such as:

1. Voltage divider. Two or more resistors connected in series can be used for a voltage divider at their junction point.
2. Current divider. Two or more resistors connected in parallel can be used for a current divider at one of the branches.
3. Bias resistor. This resistor helps to make sure the current flowing in the circuit is at minimum value.
4. Op-amp gain and feedback. Resistor is used to set the value of an op-amp’s gain and feedback externally.
5. Current limiter. This is the most common function of a resistor, to limit the flowing current in the circuit.
6. Impedance matching. Resistor is used to maximize power transmission by matching the impedance at the start and at the end of the line.
7. Current measurement. Looking at Ohm’s Law, we can use a resistor to determine how much current is flowing in the circuit.

Frequently Asked Questions