Flourescents (was: What tools do you carry, always

Fluoresent discharge tube - ...the type most often used is a slender glass tube filled with mercury vapor at low pressure, with argon added to help starting... At each end of the tube is a filament-type electrode coated with a material that easily emits electrons when heated. When the current - usually alternating current - is switched on, the filaments heat up and emit electrons, each one acting as the anode or cathode depending on the half-cycle of the current. A high voltage between the electrodes is needed to start the argon discharge, and this is done using a starter or a choke or ballast. The starter automatically breaks the circuit when the filaments have heated up, causing the choke, which is an induction coil, to produce a brief pulse of high voltage electricity. This starts the argon discharge and, very shortly, a mercury discharge. This is self sustaining, with a continuous flow of electrons between the electrodes. The radiation from the ionized vapour is strong in the ultraviolet. This falls on a coating of fluorescent material on the inside of the tube, which glows by absorbing the invisible and harmful ultraviolet and re-radiating it as vivible light. The color of this light can be chosen by suitably arranging the mix of fluorescent coating, the most common shades being 'white' and 'warm white'.