# What is the function of the resistor in a circuit? There may have 4!

We all know that the resistor can reduce the voltage, and the resistor itself consumes a certain amount of loss (heating), so to transform and reduce the voltage, it seems to use a transformer. The energy conversion efficiency of the transformer should be higher; why are there so many circuits? So many small resistors are used; is it to reduce the voltage?

## 1. Resistors are used for current limiting

To ensure that the current passing through the electrical appliance does not exceed the rated value or the specified value required for actual work to ensure the regular operation of the electrical device. A variable resistor can usually be connected in series in the circuit. When changing the size of this resistor, the magnitude of the current also varies. We call this kind of resistor that can limit the extent of the current as a current limiting resistor. For example, in the circuit of a dimmable desk lamp, a current limiting resistor can also be connected to the course to control the bulb’s brightness. And can handle the current size in the circuit by adjusting the size of the access resistor, thereby preventing the bulb’s illumination.

## 2.Resistors are used for current shunt

When several electrical appliances with different rated currents need to be connected simultaneously on the circuit’s primary circuit, a resistor can be connected in parallel at both ends of the electrical appliance with the smaller rated current. The function of this resistor is to “shunt” the wind. For example, two bulbs, A and B, and the rated currents are 0.2A and 0.4A, respectively. It cannot be directly connected to the two bulbs to the same circuit. But if we connect a suitable shunt resistor in parallel at both ends of lamp A, both lamps A and B can work typically when switch S is closed. For another example, in the experimental design of measuring resistance without a voltmeter, the practical circuit shown in Figure 3 can be designed; the shunt resistance R is used in parallel with the opposition to be measured. The primary circuit current and the current in the shunt resistance R are measured with the help of an ammeter. They are using the parallel shunt formula. Can be obtained the resistance value to be measured. If there is only one ammeter, the ammeter can be connected successively in the primary circuit or in different branches to calculate the I sum (or sum or sum) and can also be obtained.

## 3.Resistors are used to divide the voltage

Generally, the rated voltage is marked on the electrical appliance. If the power supply is higher than the rated voltage of the electrical device, it cannot directly connect the electrical device to the power supply. In this case, a resistor with a suitable resistance value can be connected in series to the electrical appliance to share a part of the voltage, and the electrical device can work under the rated voltage. We call such a resistor a voltage divider.

## 4.Resistors are used to convert electrical energy into internal energy

When a current passes through a resistor, all (or part) of the electrical energy is converted into internal energy. Electrical appliances used to convert electrical power into internal energy are called electric heaters. Such as electric soldering iron, electric stove, rice cooker, heater, etc.