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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
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.
What should be the value of R in the figure for which the current in it is zero?
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
State any two sources of errors in the meter-bridge experiment. Explain how they can be minimized.
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?
The current which flows in a galvanometer of Wheatstone bridge is directly proportional to ______
With resistances P and Q placed in the left and right gaps of a metre bridge, the balance point divides the wire in the ratio of 1/3. When P and Q are increased by 40 n each. the balance point divides the wire in the ratio of 3/5. The values of P and Q will be respectively, ______
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 a Wheatstone bridge, when the potentials at points B and D are the same, then the current through the galvanometer ______
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 ____________.
With a resistance of 'X' in the left gap and a resistance of 9 Ω in the right gap of a meter bridge, the balance point is obtained at 40 cm from the left end.
In what way and to which resistance 3 Ω resistance be connected to obtain the balance at 50 cm from the left end?
In a metre bridge experiment. the ratio of the left-gap resistance to right gap resistance is 2: 3. The balance point from the left is ______.
The metre bridge works on the principle of ______.
On interchanging the resistances, the balance point of a metre bridge shifts to the left by 10 cm. The resistance of their series combination is 1 k`Omega`. How much was the resistance on the left slot before interchanging the resistances?
What is the e.m.f of the cell C in the circuit shown in figure, if the deflection in the galvanometer is zero, the resistance of the wire is 3 `Omega`, The length of the wire is 100 cm?
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 ______.
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 ____________.
The potential difference between the points A and B in the electric circuit shown is ______.
Which among the following resistances can be determined by a metre bridge?
In the measurement of a resistance by the Wheatstone bridge, the known and the unknown resistance are interchanged to eliminate ____________.
In a balanced metre bridge, 5 Ω is connected in the left gap and R Ω in the right gap. When R Ω is shunted with equal resistance, the new balance point is at 1.6 I1 where 'I1' is the earlier balancing length. The value of 'I1' is ______
The current through 1 `Omega` resistance in the following circuit is ______.
In a Wheatstone's bridge, the resistance in the three arms are P, Q, R, and its fourth arm has a parallel combination of two resistances S1 and S2, The balancing condition of the bridge is ______
Four resistances 4Ω, 4Ω, 4Ω and 12Ω form a Wheatstone's network. Find the resistance which when connected across the 12Ω resistance will balance the network.
What is a post office box? How is the· unknown resistance measured using a post office box?
In the given Wheatstone's network, what should be the value of R for the network to be balanced?
Two resistances are connected in two gaps of a meter bridge. The null point is obtained at 20 cm from zero end. A resistance of 15 is connected in series with smaller of the two. The null point shifts to 40 cm. The smaller resistance used in is ______.
