tangent of an angle (trigonometric function). The tangent of an angle in a right triangle is the ratio of the length of the side of the triangle opposite the angle, to the length of the side adjacent to (next to) the angle.

tank circuit (electronic circuit). A resonant electronic circuit composed of a capacitor and an inductor in parallel. Electrical energy is stored in a tank circuit in the form of electromagnetic and electrostatic fields that build up and decay at a frequency determined by the capacitance and the inductance in the circuit.
tantalum. A hard, gray, or steel-blue metallic chemical element. Tantalum’s symbol is Ta, its atomic number is 73, and its atomic weight is 180.948. Tantalum is used in the manufacture of light bulb filaments, and tantalum oxide is used in electrolytic capacitors.
tantalum carbide. A compound of tantalum and carbon in a hard, crystalline form, used for making cutting tools and dies.
tantalum-foil capacitor. A type of electrolytic capacitor that uses tantalum foil for the plates. An oxide film formed on the anode, the positive plate, serves as the dielectric. Absorbent paper saturated with an electrolyte keeps the plates separated. The large capacity of a tantalum-foil capacitor is caused by the thinness of the oxide-film dielectric.
tap (thread-cutting tool). A metal-cutting tool used to cut threads on the inside of a hole. A taper tap is used to start the threads in the hole; then a plug tap is used to cut threads to almost the full depth of the hole. If it is necessary that the threads extend to the very bottom of the hole, a bottoming tap is used. The threads cut by a bottoming tap are the same from one end to the other.
tap drill. A twist drill of the correct size to drill a hole to be tapped. There is a correct tap drill for each size tap.
tape measure. A long, narrow strip of cloth, paper, or steel with graduations of inches or millimeters marked along its edge.
taper (dimensional change). A gradual change in the width or thickness of an object along its length.
taper (resistance change). The relationship between the change in the resistance of a potentiometer or rheostat and the amount of rotation of its shaft. The resistance of a linear-taper potentiometer or rheostat changes in direct proportion to the number of degrees the shaft is rotated.
tapered pin. A type of hardware used to fasten concentric tubes together or to fasten a sleeve around a solid shaft. A tapered pin is pressed into a tapered hole drilled through the components to be joined. Some tapered pins are secured in place by passing safety wire through a hole in the large end of the pin and then wrapping it around the shaft or tubes. Other tapered pins are secured with a nut screwed onto threads cut onto the small end of the pin.
tapered propeller shaft (reciprocating engine component). A propeller shaft with a tapered end that fits into a tapered hole inside the propeller hub. A tapered propeller shaft is prevented from turning in the hub by a hardened steel key that fits in matching grooves in the shaft and the hub.