Home / Products / Resistors

Resistors definition

Resistor is generally called resistance in daily life. It is a current limiting component. After a resistor is connected in a circuit, the resistance of the resistor is fixed, usually with two pins. It can limit the current flowing through the branch it is connected to. Those whose resistance value cannot be changed are called fixed resistors. Those with variable resistance are called potentiometers or variable resistors. An ideal resistor is linear, that is, the instantaneous current through the resistor is proportional to the applied instantaneous voltage. Variable resistor for voltage dividing. On the exposed resistor body, one or two movable metal contacts are pressed tightly. The contact position determines the resistance between either end of the resistor and the contact.

How to detect resistors

1.Appearance inspection

For fixed resistors, first check that the markings are clear, the protective paint is intact, there are no burns, no scratches, no cracks, no corrosion, and the resistor body is in close contact with the pins, etc. For the potentiometer, you should also check that the rotating shaft is flexible, has appropriate tightness, and feels comfortable in the hand. If there is a switch, check whether the switch operates normally.

2.Multimeter detection

Detection of fixed resistance

Use the electrical barrier of a multimeter to measure the resistance. To measure resistors with different resistance values, choose different multipliers of the multimeter. For pointer multimeters, since the indication of electrical resistance is non-linear, the greater the resistance, the denser the indication. Therefore, when choosing a suitable range, the deflection angle of the meter needle should be larger, and the indication should be between 1/3 and 2/3 of the full scale. , the reading is more accurate. If the measured resistance value exceeds the error range of the resistor, the resistance value is infinite, the resistance value is 0, or the resistance value is unstable, it means that the resistor is broken.

During measurement, be careful not to touch the two pins of the resistor with the hand holding the resistor. This will cause the resistance presented by the hand to be in parallel with the resistance being measured, affecting the accuracy of the measurement. In addition, do not use a multimeter to electrically block the resistance of the resistor in the circuit when it is powered. For online detection, the power should be cut off first, then the resistor should be disconnected from the circuit, and then measured.

Detection of fuse resistance and sensitive resistance

The fuse resistor generally has a resistance of only a few to dozens of ohms. If the measured resistance is infinite, it has been blown. You can also check the quality of the fuse resistor online and measure the voltage at both ends to ground. If one end is the power supply voltage and the voltage at the other end is 0 volts, the fuse resistor has been blown.

There are many types of sensitive resistors. Taking thermistors as an example, they are divided into positive temperature coefficient and negative temperature coefficient thermistors. For positive temperature system (PTC) thermistors, the resistance is generally not large at room temperature. Use a hot soldering iron close to the resistor during measurement. At this time, the resistance should increase significantly, indicating that the resistance is normal. If there is no change, it means The component is damaged, and the opposite is true for the negative temperature thermistor.

When the photoresistor is not illuminated (cover the light with hands or objects), the resistance value measured by the multimeter is large, and the resistance value indicated by the illuminated needle is significantly reduced. If there is no change, the component is damaged.

Detection of variable resistors and potentiometers

First, measure whether the resistance value between the two fixed terminals is normal. If it is infinite or zero ohms, or is greatly different from the nominal value and exceeds the allowable error range, it means it is damaged. The resistance value of the resistor body is normal. Then put a multimeter on it. The test lead is connected to the sliding end of the potentiometer, and the other test lead is connected to any fixed end of the potentiometer (adjustable resistor). Slowly rotate the shaft and observe whether the needle changes smoothly. When rotating from one end to the other, the resistance value changes from zero to zero. If the ohm changes to the nominal value (or vice versa), and there is no jump or jitter, it means that the potentiometer is normal. If there is a jump or jitter during the rotation, it means that the resistor body at the sliding point has poor contact.

3.Use a bridge to measure resistance

If it is required to accurately measure the resistance of a resistor, the test can be performed with a bridge (digital). Insert the resistor into the measuring end of the bridge component, select the appropriate range, and then read the resistance value of the resistor from the display. For example, when you use resistance wire to make a resistor or process a fixed resistor to obtain a more accurate resistance value, you must use a bridge to measure the resistance of the homemade resistor.

Where to buy resistors

Nantian Electronics sells different types of resistors such as: carbon composition resistors, ceramic composition resistors, chassis mount resistors (planar and wirewound), chip resistors, current sensing resistors (SMD and through hole), thin film resistors, MELF resistors, metal foil resistors (SMD).

Do resistors have polarity

In general, standard resistors do not have polarity. Resistors are passive electronic components that impede the flow of electrical current without any concern for the direction of that current. They work the same way regardless of the direction of current flow, so they are considered non-polarized components.

However, there are specialized resistors called "polarized resistors" or "directional resistors," which are designed to have polarity or direction-specific characteristics. These types of resistors are not common and are used in specific applications where the direction of current flow matters. In most electronic circuits, standard resistors are non-polarized and can be connected in either direction.

what is the potential difference across the 10 ω resistor

What size resistor for led

To determine the appropriate resistor size (resistance value) for an LED, you'll need to consider the LED's forward voltage (Vf), the supply voltage (Vs), and the desired operating current (If) for the LED. Here's how you can calculate the resistor value:

  1. Find the Forward Voltage (Vf) of the LED: This information is usually provided in the LED's datasheet. Typical values for common LEDs are around 1.8 to 3.5 volts.

  2. Determine the Desired Operating Current (If) for the LED: The desired operating current for the LED is also typically specified in the datasheet. It's usually given in milliamperes (mA). Common values are 5 mA, 10 mA, or 20 mA, depending on the LED and your brightness preference.

  3. Calculate the Voltage Drop Across the Resistor (Vr): Vr = Vs (Supply Voltage) - Vf (Forward Voltage of LED)

  4. Calculate the Resistor Value (R): R = Vr / If

Now you have all the values needed to calculate the resistor value (R) in ohms. Once you calculate R, you may choose the nearest standard resistor value available in the market.

Does resistor direction matter

In most electronic circuits, the direction or orientation of a resistor does not matter. Resistors are passive components that restrict the flow of electric current, and they are typically not polarized. This means you can connect them in either direction within the circuit, and they will perform their function effectively.

However, there are a few specific cases where resistor direction may matter:

Temperature-Dependent Resistors: Some resistors, like thermistors, are sensitive to temperature changes and exhibit different resistance values at different temperatures. For these resistors, the direction may matter if the resistor is being used in a way that relies on its temperature-sensitive properties.


Precision Resistors: In applications requiring extremely precise resistance values, such as in precision instrumentation, some high-end precision resistors may have a specified orientation or direction for optimal performance. In such cases, it's crucial to follow the manufacturer's recommendations.

Voltage Dividers: In voltage divider circuits where resistors are used to divide a voltage, the order or arrangement of resistors can affect the output voltage. Reversing the order of the resistors will change the voltage division ratio.

Noise Considerations: In high-frequency or sensitive circuits, the physical layout of components, including resistor orientation, can affect noise and interference. Careful placement of components may be necessary.

Which resistor dissipates more power

The power dissipated by a resistor depends on its resistance value and the current passing through it. Specifically, the power (P) dissipated in a resistor can be calculated using Ohm's law and the formula:

P = I^2 * R


  • P is the power in watts (W).

  • I is the current in amperes (A) flowing through the resistor.

  • R is the resistance in ohms (Ω) of the resistor.

So, to determine which resistor dissipates more power, you need to compare the values of \(R\) and \(I

  1. Higher Resistance, Same Current: If one resistor has a higher resistance (\(R\)) than the other but the same current (

  2. Same Resistance, Higher Current: If both resistors have the same resistance (\(R\)), but a higher current (

In summary, to determine which resistor dissipates more power, you need to consider both the resistance value and the current passing through it. Higher resistance or higher current will result in more power dissipation.

Electronic Parts Index
# 0 1 2 3 4 5 6 7 8 9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

We value your privacy

Our website uses cookies to ensure you are getting the best browsing experience, serve personalized content, and analyze our traffic.
By clicking "Accept Cookies", you consent to our use of cookies. Privacy Policy