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.
No matter what you call them, condoms have the same purpose. They prevent STDs (sexually transmitted diseases) and pregnancy. That's why you need to wear one every single time you have sex. Condoms are a good birth control option because they're cheap, easy to get, and you don't have to plan ahead to use them.