Current produced by thermocouples. My understanding is that the thermocouple voltage is strictly a function of the temperature. Apparently this is called the Seebeck Voltage. Like any voltage source there is an internal resistance associated with it due to real world effects.
HIV/AIDS. Condoms for HIV prevention. Condoms, when used correctly and consistently, are highly effective in preventing HIV and other sexually transmitted infections (STIs). A large body of scientific evidence shows that male latex condoms have an 80% or greater protective effect against the sexual transmission of HIV and other STIs.
Birth Control. Condoms prevent pregnancies and STDs. They create a barrier that keeps semen and other body fluids out of the vagina, rectum, or the mouth. There are condoms for men and for women -- but don't use both at the same time. One can stick to the other and pull it out of place or tear it.