What is a resistor?

What is resistance in electricity? This article will cover the basics about resistance, how to calculate resistance, and resistors.

Many people have heard of the word "resistor" when they were students, but may still not understand it. However, because they don't understand it, they are hesitant to ask people about it now. Simply put, resistance is a force that flows in the opposite direction of the current.

Resistance affects the flow of current. This article will detail the basics of resistance, how to calculate resistance, and resistors.

■ Definition of resistance

Resistance to electricity, also known as "resistance", is a force that is opposite to the direction of the current, and is an indicator of how easy it is for the current to flow. The unit is "ohm".

When there is a potential difference between terminals, current flows from a high potential to a low potential. Resistance prevents the current from flowing. The higher the resistance, the lower the current. Conversely, if the resistance becomes smaller, the current increases.

Figure 1

■ Methods for calculating resistance

This resistance can be calculated numerically from the voltage and current in the circuit.

Resistance = voltage/current

This is the formula for what is called "Ohm's Law". When the voltage is constant, the higher the current (i.e., the denominator), the lower the resistance. Conversely, the lower the current, the higher the resistance. In other words, a circuit with a high current will have a low resistance, and a circuit with a low current will have a high resistance.

Figure 2  

Typically, resistance is determined by the conductor material, temperature and length. In general, metals have lower resistance, so current passes through them more easily, but there are differences in the different types of metals, with resistance increasing in the order of silver, copper, gold, aluminum, and iron. In addition, the lower the temperature, the lower the resistance, but the higher the temperature, the higher the resistance.

In addition, the longer the distance over which the current flows, the greater the resistance. Also, the larger the cross-sectional area of a conductor, the easier it is for current to pass through and the lower the resistance; the smaller the cross-sectional area, the higher the resistance.

The relationship between the cross-sectional area of a substance and the magnitude of an electric current

Figure 3

■ Definition of resistor

Resistor is a current limiting element, after connecting the resistor in the circuit, the resistance value of the resistor is fixed generally two pins, it can limit the size of the current through the branch circuit connected to it. Resistors are used to regulate the current and voltage in a circuit, just like regulating the flow of water with a faucet. Resistors not only control the current, but also distribute the voltage in a circuit.

Figure 4

resistors

Resistors are also needed to keep electronic circuits working properly. Resistors are made of materials that make it difficult for current to pass through them, thus preventing the current in the circuit from passing through the resistor. This controls the current in the entire circuit. When the current is reduced by the resistor, the excess electrical energy is converted into heat.

There are various types of resistors, the main ones being: 

Fixed Resistors

Variable Resistor

Semi-fixed Resistors

The main types of fixed resistors are carbon film resistors and metal film resistors, depending on whether carbon or metal is used in the resistive element. The resistance value is constant. Variable resistors are resistors whose resistance value can be adjusted. Semi-fixed resistors are variable resistors used to fine-tune voltage or current.

Figure 5

Variable Resistors

■ Methods of measuring resistance

Resistance in a circuit can be measured using a digital multimeter. Digital multimeters can measure not only resistance, but also voltage and current, so digital multimeters can be used in a variety of situations. When using a digital multimeter, you should first turn on the power switch of the multimeter and turn the switch to the resistance (Ω) block.

If necessary, select the range according to the resistance of the object to be measured. Then, insert the red test lead into the "Ω" terminal and the black test lead into the COM terminal, and measure the resistance by touching each end of the resistance with the test leads. The measurement result will be displayed on the LCD screen when the measurement is performed. When the measurement is completed, unplug the test lead.

Resistance is affected by many factors such as temperature. Some digital multimeters have a temperature compensation function for resistance meters that can compensate taking into account external influences. Therefore, when purchasing a digital multimeter, it is recommended to confirm which functions it has.

■ Resistors are indispensable in order to circulate the proper amount of current.

Resistance is an indicator of how easy it is for current to flow, and is measured in "ohms" (Ω). The lower the resistance, the higher the current; conversely, the higher the resistance, the lower the current. Resistors are essential to allow the proper amount of current to flow through a circuit. Different types of resistors are used for different purposes.

To check if the resistor is working properly, a digital multimeter is required. When you need to measure the resistor, please refer to the above instructions for use.