How to find the best resistor?

Resistor

First of all what is a resistor?

A resistor is a passive two-terminal electrical component, which is mostly used to reduce current flow, to divide voltages.

A resitor

Calculate the resistance

The unit of resistance is Ohm(Ω).

It was named after a German physicist and mathematician, Georg Simon Ohm.

How to calculate the resistance?

R = U/I

What does it mean?

  • R: Resistance
  • U: Voltage
  • I: Current
Georg Simon Ohm

Use in everyday life

Let's calculate the resistance of an arbitrary consumer!

  • U = 10V
  • I = 2A
  • R = ?

R = U/I = 10V / 2A = 5Ω

What about LEDs?

LEDs are semiconductors, so the formula will be a little different here:
R = (Us - ULED) / ILED

A typical red LED has a voltage of 2V and a current of 10mA(0.01A). We power it by 5V.

Let's substitute the values:
R = (5V - 2V) / 0.01A = 300Ω