where is the positive on a cigarette lighter
Cigarette lighter receptacle The sockets and mating plugs are defined in the ANSI/SAE J563[7] specification. For the 12 volt systems, the "contact point", which is the center part of the plug when viewed end-on, carries the positive voltage, whereas the "can" part, which is the outer part of the connector, carries the negative voltage (which is the "ground" connection for most automobiles, which have a negative ground electrical system).
AS/NZS 3112 The plug pictured on the left, as used in Australia, New Zealand, Fiji, Papua New Guinea and many Pacific Island countries, has two flat pins forming an inverted V-shape plus a vertical earthing pin. These flat blades measure 6.35 by 1.6 mm (1⁄4 by 1⁄16 in) with the Active and Neutral pins 17.35 mm (11⁄16 in) long set 30° to the vertical and the vertical Earth pin being 20 mm (0.787 in) in length.[2] The pins are arranged at 120° angles around a common midpoint, with the Active and Neutral centred 7.92 mm (5⁄16 in) from the midpoint, and the Earth pin centred 10.31 mm (3⁄8 in) away.[2]