A Wheatstone bridge is specifically designed for the accurate measurement of small and unknown resistances. It operates on the principle of balancing two legs of a bridge circuit, enabling precise determination of resistance values. Potentiometer: Used to measure potential difference or electromotive force (emf), not to measure resistance directly. Rheostat: A variable resistor utilized to control current, rather than for measuring resistance. Wheatstone Bridge: The most effective method for measuring very small resistances.