2
\$\begingroup\$

I am trying to figure out how electricity works and I wonder why do electronics components have the maximum voltage limit?

Why does the voltage matter? Isn't it the current that can 'kill' the component?

For example if I have an LED with a maximum voltage of 2V powered by a 5V source. If I put enough resistance in the circuit - it will effectively lower the current and the LED will be working fine, the voltage would stay the same though. Which means the LED is working fine beyond the voltage limit.

I would really appreciate if someone could clarify this.

\$\endgroup\$
2
  • 1
    \$\begingroup\$ A good example is the maximum reverse voltage for an LED. No current flows, but it will fail at a certain reverse voltage (and then current will flow). Some things need a maximum current, some a voltage, most things need both. \$\endgroup\$
    – tomnexus
    Jul 5, 2015 at 8:55
  • \$\begingroup\$ Yes but the voltage over the LED decreases accordingly. Voltage over the LED is the independent variable \$\endgroup\$ Aug 18, 2022 at 14:04

3 Answers 3

3
\$\begingroup\$

You most probably don't have a LED 'with a maximum voltage of 2V when powered from a 5GV source', but a LED that is rated for a maximum of 20 mA.

Components that have a low resistance, and particularly ones that approximately drop the same voltage over a wide current range, are rated for a maximum current, not a maximum voltage.

For most components, voltage and current have a fixed relation that can be found in their datasheet. In most cases it is their product (power P = V * I) through power dissipation that causes a temperature rise above what the integrated circuit material is rated and causes it to fail. The maximum could be expressed in either power or voltage. But when component and temperature variations can cause the same voltage to cause widely different currents, it makes more sense to express the maximum as a current. OTOH, if above a certain voltage breakdown will occur, but the breakdown current is not easy to specify, it makes more sense to express the maximum as a voltage.

Summary: the maximum is generally expressed in the unit that is (for the components at hand) most stable.

\$\endgroup\$
2
  • \$\begingroup\$ Great explanation, thank you! My main problem was that I did not understand the voltage drops, your answer makes it much clearer, I am picking it as the solution. \$\endgroup\$
    – YemSalat
    Jul 9, 2015 at 16:16
  • \$\begingroup\$ A 5GV source would be a sight to behold. \$\endgroup\$
    – user253751
    Jan 31, 2020 at 11:18
1
\$\begingroup\$

From what it sounds like you are saying, You are putting resistance in series to lower the current to the LED. The LED and resistors are seeing 5V but the LED is not seeing the 5V now. At the appropriate current it will only be seeing 2V. The resistor will be seeing 3V and the circuit will be balanced 2+3=5. When devices are in series they will always see the same current.

\$\endgroup\$
0
\$\begingroup\$

While current represents the amount of units of charge that pass through a point in a given amount of time, voltage represents the amount of energy that each unit of charge possesses. And energy causes things to happen. Such as heating. And insulation breaking down. So too much voltage and bad things will happen.

\$\endgroup\$
7
  • \$\begingroup\$ So if I were to proportionally increase the voltage and resistance in the circuit the LED would not get brighter, but will get hotter. Is that correct? \$\endgroup\$
    – YemSalat
    Jul 5, 2015 at 4:21
  • \$\begingroup\$ The LED has its own non-ohmic resistance. Attempting to increase the voltage across it will increase the current as well. \$\endgroup\$ Jul 5, 2015 at 4:22
  • \$\begingroup\$ Yep, I understand that. What I am saying is that if I increased the voltage and added more resistors to the circuit, so that the current stays at the same level. Would that make the LED get hotter? Even though the current is the same? \$\endgroup\$
    – YemSalat
    Jul 5, 2015 at 4:27
  • \$\begingroup\$ No, because the voltage across it will remain the same. The resistors on the other hand would get hotter (overall). \$\endgroup\$ Jul 5, 2015 at 4:27
  • \$\begingroup\$ Why does the voltage on the LED stay the same when I increase it on the circuit? \$\endgroup\$
    – YemSalat
    Jul 5, 2015 at 4:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.