I will keep this brief a tattoo machine is basically an old fashioned doorbell. to coils wired together with a resistance of 2 ohms, generally a 47uf 50v electrolytic axial capactior. the contact is a spring and copper screw. the circuit opens and closes rapidly, 105hz to 145hz. my question is heat produced by electromagnets and the causes and or ways to reduce heat. the yoke is the frame base of the machine which is 1018cr steel as well as the coil cores themselves.