A wheatstone bridge is used to determine the value of unknown resistance X by adjusting the variable resistance Y as shown in the figure. For the most precise measurement of X, the resistances P and Q :

Question

A wheatstone bridge is used to determine the value of unknown resistance X by adjusting the variable resistance Y as shown in the figure. For the most precise measurement of X, the resistances P and Q : 1. do not play any significant role 2. should be approximately equal to 2X 3. should be approximately equal and are small 4. should be very large and unequal

Doubtly AI · Accepted Answer

Answer: 3. should be approximately equal and are small A Wheatstone bridge is most sensitive when all four arms have comparable resistance, so P and Q should be roughly equal to each other (and of the order of X and Y). Small values of P and Q also keep the bridge current large enough for the galvanometer to show a clear deflection and make the balance point easy to detect. The official key is option (3): P and Q approximately equal and small. Options (1) and (4) ignore the sensitivity condition, and (2) fixes an arbitrary value 2X .

A wheatstone bridge is used to determine the value of unknown resistance X by adjusting the variable resistance Y as shown in the figure. For the most precise measurement of X, the resistances P and Q :

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