What does the odometer of an automobile measure ?

Explanation

A fuel gauge in an automobile uses variable resistance and current to measure the level of liquid fuel in the tank. The float level in the tank adjusts the resistance of a variable electric resistor, corresponding to which current flows through the fuel gauge, which inturn, deflects the pointer on the scale of fuel gauge.
When fuel tank is empty, the electric resistors offers maximum resistance. In this situation, the pointer shows minimum deflection, marked empty (denoted b y E) on gauge meter. When tank is full, the electric resistor offers minimum resistance and the pointer shows maximum deflection, marked full (denoted by F) on gauge meter.
When the fuel in the tank is partly empty, the resistance of electric resistor is in between minimum and maximum. The corresponding value of current produces appropriate deflection of the gauge pointer giving the idea of fuel present in the tank.