# What resistor is needed to make enough heat from a PP3 9V Battery to pop a ballon?

Discussion in 'Power Electronics' started by dixie48, Sep 15, 2010.

1. ### dixie48

1
0
Sep 15, 2010
What size resisor would i need to generate enoughheat from a pp3 9 Volt Battery to pop a Ballon

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,309
2,738
Jan 21, 2010
determine the short-circuit current from the battery and then pick a resistor that will draw about half of that current across the battery voltage.

Then get the smallest size resistor you can of this value (probably a surface mount type).

As long as the power isn't applied long enough to make it smoke, you should get enough heat to pop the balloon.

Last edited: Sep 15, 2010
3. ### Resqueline

2,848
2
Jul 31, 2009
The procedure suggested by steve will give you the fastest possible pop (possibly around a tenth of a second?). R = 4.5V / Isc.

I don't know what temperature it takes to pop a balloon, but here are some practical values of approximately what to expect from an 1/8W (0,125W) resistor in free air.:

150 ohms = 60mA = 0.5W = 90 degrees C.
82 ohms = 110mA = 1W = 150 degrees C.
56 ohms = 150mA = 1.4W = 200 degrees C.

I'd suggest to try using an easily manageable 47 ohm 1/8W resistor, which will yield a considerable temperature but which still won't go up in smoke.

Last edited: Sep 16, 2010
4. ### THUNDERBOLT

22
0
Aug 29, 2010
How did you get 150°C and the other values please??

That would be handy to know, I just don't know how to do that calculation. Thanks

5. ### Resqueline

2,848
2
Jul 31, 2009
I didn't calculate the temperatures, I measured them with a thermal image camera. I didn't calibrate it though so please consider the values as being approximate.
Many resistor datasheets will present a surface temperature at the rated power. The other values (resistance, current, power) are from Ohms law. See Tutorials above.  