What Is Resistance/Load?
Resistance is the action of restraining an external force.
Load resistance in industrial products suppresses the current flowing in an electric circuit. In a DC circuit, the resistance R is represented by R=V/I from the formula V=IR. If the voltage between points A and B is V and the current flowing is I, then the resistance between them is R. The unit is ohm (symbol: Ω) .
To change the perspective, if the voltage between points A and B is V and the value of the current is I, the value of R can be found by V/I when choosing the value of the resistance to be installed. In AC circuits, resistance is called impedance and is represented by the symbol Z. The unit of measurement is also ohm. R in a DC circuit can be replaced by Z and expressed as V = IZ.
In an AC circuit, the impedance component of a coil or capacitor is called reactance, which is inductive reactance in the case of a coil and capacitive reactance in the case of a capacitor, and both work to block the flow of current. In AC circuits with coils and capacitors, the calculation of impedance becomes more complex and includes a complex number of items expressed as a phase difference component from the resistance R.
Types of Resistance / Load
There are variable resistors as opposed to fixed resistors. Variable resistors have a structure in which the resistance increases in proportion to the distance between two points, and usually one side is fixed and the other side is slid to change the resistance.
There are two main types of structures: rotary type and linear type. The resistors mounted on a surface-mounted board by melting solder in a reflow oven are called chip resistors, while the types with lead wires are called chip resistors.
How to Select Resistance / Load
For lead wire type resistors, the most commonly used and relatively inexpensive carbon film resistors are selected by the resistor material.
However, the resistance value may be affected by the ambient temperature, resulting in current noise or poor frequency characteristics, in which case, a slightly more expensive metal film resistor type should be selected.
There is also a wire-wound resistor type that excels in heat resistance, but because of its inductance component, it must be used with caution in high-frequency circuits. On the other hand, there are also metal resistor types with small inductance components and resistors with fuse functions, so it is important to select the appropriate type that meets the requirements of circuit design.