UnScramble this Word: b t s e a l a?

Questions

A device used to change the voltage of alternating currents is a ______?

A dime has how many ridges around the edge?

A dolphin can remember a specific ______ better than a human?

A famous RAH novel, as well as a number believed to be cursed?

A favourite spot for vampires to bite (that's one hell of a hickey!)?