Advertisements
Advertisements
प्रश्न
A resistance R is to be measured using a meter bridge. Student chooses the standard resistance S to be 100Ω. He finds the null point at l1 = 2.9 cm. He is told to attempt to improve the accuracy. Which of the following is a useful way?
विकल्प
He should measure l1 more accurately.
He should change S to 1000Ω and repeat the experiment.
He should change S to 3Ω and repeat the experiment.
He should give up hope of a more accurate measurement with a meter bridge.
उत्तर
He should change S to 3Ω and repeat the experiment.
Explanation:
⇒ `R = S(l_1/(100 - l_1)) = 100 2.9/97.1` = 2.98Ω
In this problem, the balanced Wheatstone bridge is to be used.
Condition of balanced wheatstone bridge: The bridge is said to be balanced if the ratio of the resistances in the same branch is equal `R/S = (l_1/(100 - l_1))`
Wheatstone bridge is an arrangement of four resistances which can be used to measure one unknown resistance of them in terms of rest.
The percentage error in R can be minimised by adjusting the balance point near the middle of the bridge, i.e., when l, is close to 50 cm. This requires a suitable choice of S.
Since, `R/S = (l_1/(100 - l_1))`
Since here, R : S = 2.9 : 97.1 then the value of S is nearly 33 times that of R. In order to make this ratio 1:1, it is necessary to reduce the value of S almost 1/33 times, i.e., nearly 3Ω.
APPEARS IN
संबंधित प्रश्न
With the help of a labelled diagram, show that the balancing condition of a Wheatstone bridge is
`"R"_1/"R"_2 = "R"_3/"R"_4` where the terms have their usual meaning.
The current which flows in a galvanometer of Wheatstone bridge is directly proportional to ______
In the circuit shown, a metre bridge is in its balanced state. The metre bridge wire has a resistance 0.1 ohm/cm. The value of unknown resistance X and the current drawn from the battery of negligible resistance are ____________.
In the metre bridge experiment shown in the figure, the balance length AC corresponding to null deflection of the galvanometer is x. What would be the balance length if the radius of the wire AB is doubled?
In Wheatstone's network p = 2 `Omega` , Q = 2 `Omega`, R = 2 `Omega` and S = 3 `Omega`. The resistance with which S is to be shunted in order that the bridge may be balanced is ______.
The resistances in left and right gap of a metrebridge are 20 `Omega` and 30 `Omega` respectively. When the resistance in the left gap is reduced to half its value, the balance point shifts by ______.
In the network shown cell E has internal resistance r and the galvanometer shows zero deflection. If the cell is replaced by a new cell of emf 2E and internal resistance 3r keeping everything else identical, then ______.
In the measurement of a resistance by the Wheatstone bridge, the known and the unknown resistance are interchanged to eliminate ____________.
In the given circuit, if I = 100 mA and I1 = I4 = 60 mA, the currents I3 and I5 are ______.
What is a post office box? How is the· unknown resistance measured using a post office box?
