Old 13th Apr 2019, 12:58
  #3 (permalink)  
Join Date: Jun 2009
Location: UK
Posts: 74
If you have no training or experience in this please leave large charged capacitors alone !

The resistor and the capacitance together determine the rate of discharge:

A slow discharge rate may be adequate in some circumstances which leads to a high resistance value and lower wattage resistor being suitable. This also disturbs the circuit less

If (e.g. for safety purposes) a rapid discharge is needed consider lower value resistors, resulting in greater heat dissipation and greater effect on the circuit if permanently in circuit. If connecting a resistor specifically to discharge consider sparks and potential for the resistor leads to weld on.

A common error in high voltage systems is to forget that resistors also have a breakdown voltage rating that may be surprisingly low in some applications

If you multiply the capacitor value in Farads by the resistor value in Ohms you get the 'Time constant' which is roughly the time in seconds to discharge the capacitor by 60% (the discharge rate getting slower and slower as it continues)

From this you see that any resistor value will discharge the capacitor eventually (assuming it doesn't burn out along the way) but for practical use you need to include the time you have and the capacitor size vs resistor power you see to find if there might be a suitable 'all purpose resistor in your work
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