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प्रश्न
Explain with a neat circuit diagram. How you will determine the unknown resistances using a meter bridge.
Explain with a neat circuit diagram how will you determine unknown resistance ‘X’ by using meter bridge.
With the help of neat labelled circuit diagram explain the use of metre bridge to determine unknown resistance.
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उत्तर
Construction: Metrebridge consists of a one-metre-long wire of uniform cross-section, stretched on a metre scale which is fixed on a wooden table. The ends of the wire are fixed below two L shaped metallic strips. A single metallic stripe separates the two L-shaped strips leaving two gaps, left gap and right gap. Usually, an unknown resistance X is connected in the left gap and a resistance box is connected in the other gap. One terminal of a galvanometer is connected to point C on the central strip, while the other terminal of the galvanometer carries the jockey (J). Temporary contact with the wire AB can be established with the help of the jockey. A cell of emf E along with a key and a rheostat is connected between points A and B.
Working: A suitable resistance R is selected from the resistance box. The jockey is brought in contact with AB at various points on the wire AB and the balance point (null point), D is obtained. The galvanometer shows no deflection when the jockey is at the balance point (point D). The distances lx and lR of the null point from the two ends of the wire are measured.
Then, using the balancing conditions,
`X/R = R_(AD)/R_(DB)` ...(1)
where RAD and RDB are the resistances of parts AD and DB of the wire, respectively.
If l is the length of the wire, ρ is its specific resistance, and A is its area of cross-section, then
`R_AD = (rhol_x)/A` ...(2)
`R_DB = (rhol_R)/A` ...(3)
From equations (1), (2) and (3),
`X/R = R_(AD)/R_(DC) = (rhol_x/A)/(rhol_R/A)`
∴ `X/R = l_x/l_R`
∴ X = `l_x/l_R R`
Thus, knowing R, lx and lR, the value of the unknown resistance can be determined.
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संबंधित प्रश्न
Four resistances 4Ω,8Ω,XΩ, and 6Ω are connected in a series so as to form Wheatstone’s
network. If the network is balanced, find the value of ‘X’.
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.
Obtain the balancing condition for the Wheatstone bridge arrangements as shown in Figure 4 below:
Choose the correct:
Four resistances 10 Ω, 10 Ω, 10 Ω and 15 Ω form a Wheatstone’s network. What shunt is required across 15 Ω resistor to balance the bridge
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The current which flows in a galvanometer of Wheatstone bridge is directly proportional to ______
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In a metre bridge experiment, the null point is obtained at 20 cm from one end of the wire when resistance X is balanced against another resistance Y. If X < Y, then where will be the new position of the null point from the same end, if one decides to balance a resistance of 4X against Y?
In a metre bridge, the gaps are closed by two resistances P and Q and the balance point is obtained at 40 cm. When Q is shunted by a resistance of 10 Ω, the balance point shifts to 50 cm. The values of P and Q are ______
In Wheatstone's bridge P = 7 ohm, Q = 12 ohm, R = 3 ohm and S = 8 ohm. How much resistance must be put in parallel to the resistance S to balance the bridge?
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 ______.
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When the value of R in the balanced Wheatstone bridge, shown in the figure, is increased from 5 `Omega` to 7 `Omega`, the value of s has to be increased by 3 `Omega` in order to maintain the balance. What is the initial value of S?
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 ______.
Which among the following resistances can be determined by a metre bridge?
Two resistances prepared from the wire of the same material having diameters in the ratio 2 : 1 and lengths in the ratio 2 : 1 are connected in the left gap and right gap of Wheatstone's meter bridge respectively. The distance of the null point from the left end of the wire is ______
ln, a Wheatstone network, P = Q = R = 8 `Omega` and S is 10 `Omega`. The required resistance to be connected to S so that network is balanced is ______.
The resistances in left and right gap of a meter-bridge are 3 `Omega` and 5 `Omega` respectively. When the resistance in the left gap is increased by 10%, the balance point shifts nearly by ______.
When an unknown resistance 'X' is connected in the left gap of a meter bridge and a known resistance 'R' in the right gap, a null point is obtained at 40 cm from the left end. If a 2 Ω resistance is connected in series with 'X' the null point shifts towards the right by 10 cm, with some resistance in the right gap. The value of 'X' must be ______
The figure below shows a balanced Wheatstone network. If it is disturbed by changing P to 22Ω, then which of the following steps will bring the bridge again to a balanced state?
With an unknown resistance X in the left gap and a resistance of 30 Ω of the gap of a metre bridge, the null point is obtained at 40 cm from the left end of the wire. Find the unknown resistance. Also, find the shift in the null point when resistance in each gap is shunted by a resistance of 8 Ω.
Draw a neat labelled diagram of Kelvin's meter bridge circuit for the measurement of galvanometer resistance.
