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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
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
In Wheatstone’s meter-bridge experiment, the null point is obtained in the middle one-third portion of the wire. Why is it recommended?
State any two sources of errors in the meter-bridge experiment. Explain how they can be minimized.
Four resistances 4 Ω, 8Ω, XΩ and 12Ω are connected in a series to form Wheatstone’s network. If the network is balanced, the value of X is ______.
In a meter bridge, two unknown resistances R and S, when connected between the two gaps, give a null point is 60 cm from one end. What is the ratio of R and S?
In conversion of moving coil galvanometer into an ammeter of required range, the resistance of ammeter, so formed is ______.
[S = shunt and G = resistance of galvanometer]
Two wires A and B of equal lengths are connected in left and right gap of a meter bridge, null point is obtained at 40 cm from left end. Diameters of the wire A and B are in that ratio 3 : 1. The ratio of specific resistance of A to the of B is ____________.
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 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 ______.
In the Wheatstone bridge, (shown in the figure) X = Y and A > B. The direction of the current between a and b will be ____________.
A resistance of 5 `Omega` is connected in the left gap of a metre bridge and 15 `Omega` in the other gap. The position of the balancing point is ____________.
In following figure, a current of 1.4 A flows towards the bridge circuit. The current in 2 n resistor is ______.
The potential difference between the points A and B in the electric circuit shown is ______.
In the meter bridge experiment, a null point was obtained at a distance of ℓ from the left end. The values of resistances in the left and right gaps are doubled and then interchanged. The new position of a null point is ______
The current through 1 `Omega` resistance in the following circuit is ______.
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 ______
- Assertion (A): The given figure does not show a balanced Wheatstone bridge.
- Reason (R): For a balanced bridge small current should flow through the galvanometer.
In the given circuit, if I = 100 mA and I1 = I4 = 60 mA, the currents I3 and I5 are ______.
Draw a neat labelled diagram to determine unknown resistance using a meter bridge.
Find the radius of the wire of length 25m needed to prepare a coil of resistance 25Ω. (Resistivity of material of wire is 3.142 x 10-7Ωm)
Write balancing condition of a Wheatstone bridge.
