Advertisements
Advertisements
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.
Advertisements
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.
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.
Obtain the balancing condition for the Wheatstone bridge arrangements as shown in Figure 4 below:
In Wheatstone’s meter-bridge experiment, the null point is obtained in the middle one-third portion of the wire. Why is it recommended?
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, the balance point is found to be at 39.5 cm from the end A when the resistor R is 12.5 Ω (right gap).
a) Determine the resistance of X (left gap).
b) Determine the balance point of the bridge if X and R are interchanged?
c) What happens if the galvanometer and cell are interchanged at the balance point of the bridge?
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, ______
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 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 ______.
ln the metre bridge experiment, one metre long wire acts as ____________.
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?
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 ______.
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 ______
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 ______
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 ______
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 ______.
The current through 1 `Omega` resistance in the following circuit is ______.
Explain the use of Wheatstone's metre bridge to determine an unknown resistance.
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?
The current passing through the battery in the given circuit is:
In a Wheatstone’s bridge, three resistances P, Q and R connected in the three arms and the fourth arm is formed by two resistances S1 and S2 connected in parallel. The condition for the bridge to be balanced will be ______.
