Resistors

A resistor opposes the current through it and turns that energy into heat. Fixed resistors differ by the material they are made of and the power they can handle; potentiometers and trimpots are adjusted by hand. LDRs, thermistors and varistors change value with light, temperature or voltage.

11 types3 groupsSymbol IEC

Fixed

CF 1/4 W (CFR-25)

Carbon film resistorGeneral-purpose circuits, LED current limiting and dividers

Power: 0.25 W
Tolerance: ±5%
Range: 1 Ω – 10 MΩ

MF 1/4 W ±1% (MFR-25)

Metal film resistorPrecision measurement, stable dividers and low-noise audio circuits

Tolerance: ±1%
Power: 0.25 W
Temp. coeff.: ±50–100 ppm/°C

5 W axial wire-wound

Wire-wound resistorHigh power, current sensing (shunt) and low-value resistors

Power: 1–10 W
Tolerance: ±1% · ±5%
Range: 0.1 Ω – 10 kΩ

SQP series 5 W

Cement (power) resistorResistors dissipating several watts: load, discharge, current limiting

Power: 2–20 W
Tolerance: ±5%

0805, code 103 = 10 kΩ

SMD chip resistorReady-made boards and mass production; small area, automatic assembly

Package: 0805 / 0603
Power: 0.125 W (0805)
Tolerance: ±1% · ±5%

4609X-101-103 (8 × 10 kΩ, common pin)

Resistor network (SIP)Many resistors of the same value: pull-up lines, LED groups

Pin: 9 (8 resistors + common)
Tolerance: ±2%
Power: ≈0.2 W / resistor

Adjustable

16 mm rotary pot, B10K

PotentiometerAdjusting values such as volume, brightness or speed by hand

Value: 10 kΩ
Curve: B (linear) · A (log)
Tolerance: ±20%

3296W (25 turns) · 3362P (single turn)

TrimpotValues set once on the board and then left alone

Value: 10 kΩ (103)
Power: 0.5 W
Tolerance: ±10%

Sensing and protecting

GL5528

LDR (photoresistor)Simply sensing whether the surroundings are light or dark

At 10 lux: 8–20 kΩ
In the dark: ≥ 1 MΩ
Power: max. 100 mW

NTC 10 kΩ, B = 3950 K (MF52 type)

Thermistor (NTC/PTC)Measuring temperature, or protecting against overcurrent and heating

At 25 °C: 10 kΩ
B value: 3950 K
Tolerance: ±1%

14D471K (mains type)

VaristorProtecting the circuit from sudden voltage spikes

Varistor voltage: 470 V (±10%)
Body: 14 mm disc

Which one should I choose?

If you are limiting LED current or building a general circuit

Carbon film resistor

Cheap and available everywhere; 5% tolerance is enough.

If you're making a measurement or a precision voltage divider

Metal film resistor

1% tolerance, low noise and little change with temperature.

If more than 1 W of power will be dissipated in the resistor

Cement (power) resistor

The big ceramic body dissipates heat safely.

If you will change the value by hand often

Potentiometer

Adjustable at any time by turning the shaft.

For an adjustment you set once and leave

Trimpot

Takes little space on the board, does not turn by accident.

If the circuit should react to light

LDR (photoresistor)

Resistance falls as light increases; suits simple threshold detection.

Compare11 types · 5 features

Type	Value	Tolerance	Power	Price	Typical use
Carbon film resistor	Fixed	±5%	0.25 W	Very low	General purpose, LED
Metal film resistor	Fixed	±1%	0.25–0.6 W	Low	Precision divider, measurement
Wire-wound resistor	Fixed	±1% · ±5%	1–10 W	Medium	Shunt, load resistor
Cement (power) resistor	Fixed	±5%	2–20 W	Low	Load, discharge
SMD chip resistor	Fixed	±1% · ±5%	0.063–0.25 W	Very low	Ready-made boards
Resistor network (SIP)	Fixed (8 pcs)	±2%	≈0.2 W / resistor	Low	Pull-up groups
Potentiometer	Adjusted by shaft	±20%	≤ 0.5 W	Low	Volume, brightness adjustment
Trimpot	Screwdriver-adjustable	±10%	0.5 W	Low	Calibration
LDR (photoresistor)	Changes with light	Wide spread	≤ 100 mW	Very low	Light sensing
Thermistor (NTC/PTC)	Changes with temperature	±1% · ±5%	Very small (mW)	Very low	Measuring temperature
Varistor	Changes with voltage	±10%	Pulse energy (J)	Low	Overvoltage protection

Typical values; vary by manufacturer and series.