1.Explain the principle on which the Wheatstone bridge works. Show how it could

be used to measure the resistance of a busbar joint by comparison with a standard 0.1 _ resistor.

2. Draw a schematic circuit diagram of a Wheatstone bridge arranged for resistance measurement. Prove the relationship between the resistances at ‘balance’. Set out resistances, labelling each with its value, representing a bridge at balance when the measured resistance is 1.752 _. The variable-resistor dials give units, tens, hundreds and thousands, 0–10 of each; the ratio arms can each be set at 10, 100, 1000 or 10 000 _.