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
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.
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
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.
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?
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 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 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 ______.
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 ____________.
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 ______
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 ______
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 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 ______
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?
The measurement of an unknown resistance R is to be carried out using Wheatstones bridge (figure). Two students perform an experiment in two ways. The first students takes R2 = 10 Ω and R1 = 5 Ω. The other student takes R2 = 1000 Ω and R1 = 500 Ω. In the standard arm, both take R3 = 5 Ω. Both find R = `R_2/R_1 R_3` = 10 Ω within errors.
- The errors of measurement of the two students are the same.
- Errors of measurement do depend on the accuracy with which R2 and R1 can be measured.
- If the student uses large values of R2 and R1, the currents through the arms will be feeble. This will make determination of null point accurately more difficult.
- Wheatstone bridge is a very accurate instrument and has no errors of measurement.
Explain the use of Wheatstone's metre bridge to determine an unknown resistance.
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:
A battery of 6 V is connected to the circuit as shown below. The current I drawn from the battery is:
