# A 2.2k resistor is rated at '1/2 W'. What is the highest voltage you could apply to the resistor without damage to it from overheating?

Would appreciate any help! Thank you

Update:

Hi thank you for the answers, just to clarify, the resistor is 2.2 ohms, not 2.2 thousand ohms. The answer given is also 33V. I tried the equation you provided morningfox but I came up with v = sqrt1.1

Any more help would be greatly appreciated, I'm struggling on this one

Relevance

watts= volts * amps

Volts = ohms * amps

So watts = volts^2 / ohms

In this problem, you have 0.5 W = V^2 / 2200.

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The original question clearly had 2.2k.  "k" means kilo, as in thousand. Changing the question like you did is called "bait and switch", and is generally regarded as unfair. It's not a "clarification", it is a change to a different question. What next? Are you going to give another "clarification" ... it wasn't 1/2 W, it was 1/2 kilowatt?

• @Ray:  K when used with resistances, means kilo.  Kilo means thousand.  2.2kΩ means 2.2 kilohms which means 2200 ohms.

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• Anonymous
3 weeks ago

With R = 2.2k ohms, E = 33 v

With R = 2.2 ohms, E = 1.05 v

Approximately

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• watts= volts * amps

Volts = ohms * amps

So watts = volts^2 / ohms

In this problem, you have 0.5 W = V^2 / 2200.   hh

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• Most half watt resistors have voltage ratings of 350V . There are a few that will take 500 to 600 volts. There is also high voltage metal film types that can operate with 2.5kV.

Source(s): Farnell, Rapid Electronics, Digikey.
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• Let me work backwards from the answer, assuming R is unknown.

P = E^2/R

0.5 = 33^2/R

R = 33^2/0.5 = 1089*2 = 2178, which is approximately 2.2k

If the problem says 2.2 ohms, there's probably a typo, and it's supposed to be 2.2k ohms.

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• p=E^2/R  >>.5=E^2/2.2 >>2.2*.5=1.1=E^2

sqrt(1.1)=1.05 V  I=1.05/2.2=.477A

check .477*1.05=.5W

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• Anonymous
1 month ago

Use Watts = V^2/R

0.5 = V^2/2200

V^2 = 2200 x 0.5

V^2 = 1100

V = sqr Root of 

V = 33.16V

V = 33V

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• Anonymous
1 month ago

E=IR so you could use a shortcut and just cut the "R" in half (because of the 0.5W) and that would be 1100 volts

• 1100 volts would result in a current of 0.5 amps. Power would be 550 watts, not 0.5 W. The resister would blow up, or melt very fast.

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