I have 10 x 100 ohm, 1/4 watt resistors in parallel, to get a total resistance of 10 Ohms.

I do not have a datasheet for these, so I cannot look up the maximum ratings or anything like that, so I just need some general advice. I have tried searching, but this is for one resistor, not 10 in parallel.

I wanted to put a 10 watt load through all of them.

Is this safe for them?

If it is not, what is the maximum wattage I could put through all of them in total?

Is there anything that I can do to increase their wattage, like adding a heatsink?

Note, I have run out of other resistors, so I only have the 100 ohm ones.

  • 4
    \$\begingroup\$ 5V / 10ohms is only 500mA mate. You need 2.5 ohms to squeeze 2A from a 5V supply. \$\endgroup\$ – KyranF Nov 7 '14 at 20:59
  • \$\begingroup\$ George, is there something that's stopping you from using resistors with higher power rating? \$\endgroup\$ – Nick Alexeev Nov 7 '14 at 21:03
  • 3
    \$\begingroup\$ The good news though is that 5V across 10 ohms will dissipate 2.5W, and 2.5W spread across 10 equal resistors is 0.25W each ... \$\endgroup\$ – brhans Nov 7 '14 at 21:04
  • \$\begingroup\$ Why the downvotes? Thanks for the answers :) \$\endgroup\$ – George Nov 7 '14 at 21:05

The power ratings simply add, assuming that each resistor has the same cooling in the set as it would have individually. If they're all bundled close together, you'll have to derate them. So, ten 0.25-watt resistors is equivalent to one 2.5-watt resistor.

If you want to overload them, you might try immersing them in mineral oil. Back when ham radio operators built things like homemade dummy loads, it was said that you could put about 10× the power through a resistor if it was immersed in oil. So you could build a very nice, low-inductance 200W dummy load by connecting ten 510-Ω, 2-W carbon composition resistors in parallel and immersing the whole assembly in a paint can filled with oil. (IIRC, Heathkit even sold such a kit, called the "Cantenna".)

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