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Blowing Up a Resistor

Created on: 11 December 2012

By applying too high a voltage to a resistor, the resistor will draw too much current. This causes excessive power to be dissipated in the resistor which makes it go up in flames and a cloud of smoke as this video shows.

Can't see the video? View on YouTube →

If you want to try and repeat this experiment yourself, first read the Warnings and Disclaimer at the bottom of this article.

How It Works

In the video, a 10Ω ¼W resistor and 12V from a PC power supply is used. (That's a 10 ohm quarter watt resistor and a 12 volt power supply).

The power that is dissipated in the resistor is calculated by multiplying the voltage across the resistor by itself and then dividing that result by the value of the resistor. In our example this is (12V × 12V) ÷ 10Ω = 14.4W (14.4 Watts).

The little resistor is only rated at ¼W (0.25 Watts), but we are attempting to dissipate 14.4 Watts into it, that is 14.15 Watts too much! This is why you see the smoke and flame.

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The Mathematics

The equation for calculating the power that is dissipated in the resistor is:

P = V²/R

Which is the same as P = (V × V) ÷ R

P is the power dissipated in the resistor
V is the voltage across the resistor
R is the resistance of the resistor

The current flowing though the resistor can be calculated using Ohm's law:

I = V ÷ R

In our example, 1.2A tries to flow through the resistor.

Warnings and Disclaimer

Do not try this at home, there is a fire danger and danger of burning yourself, others or property. Fumes and smoke emitted by the resistor may be harmful.

If you do try to burn out a resistor, then:

  • Do it in a well ventilated area that is free of flammable materials, liquids, vapours and gasses.
  • Use a fire proof surface.
  • Have a fire extinguisher and first aid kit nearby.
  • Children must be supervised by an adult.
  • Be careful not to burn yourself on the resistor. It will get hot as soon as the power is applied to it. It may still be hot for a while after burning out.

Use this information at your own risk. The information is provided as-is and is not claimed to be fit for any purpose.

Starting Electronics and its authors will not take any responsibility for any damages or death resulting from the use of this information. You use this information entirely at your own risk.