A voltmeter is an instrument used for measuring electrical potential difference between two points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an analog to digital converter. The first digital voltmeter was invented and produced by Andrew Kay of Non-Linear Systems (and later founder of Kaypro) in 1954.
A rheostat is a device which is used to vary the resistance in an electrical circuit without interrupting the circuit. Rheostats are used to set lighting levels for comfort or mood, allowing people to change light levels without needing to change lights. English physicist Sir Charles Wheatstone invented the rheostat in 1843. POTENTIOMETER
A potentiometer informally a pot, is a three-terminal resistor with a sliding contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat. A potentiometer measuring instrument is essentially a voltage divider used for measuring electric potential (voltage); the component is an implementation of the same principle, hence its name. German inventor Johann Poggendorff designed the first potentiometer in 1843 RESISTORS
A resistor is a component of an circuit that resists the flow of electrical current. It has two terminals across which electricity must pass, and it is designed to drop the voltage of the current as it flows from one terminal to the other. Resistors are primarily used to create and maintain known safe currents within electrical components. Resistance is measured in ohms, after Ohm's law. The Resistance was discovered by the year 1827 from Georg Simon Ohm, a German electrician. RESISTANCE BOX
A resistance decade box or resistor substitution box is a unit containing resistors of many values, with one or more mechanical switches which allow any one of various discrete...