X = [R(100-l)]/L (ohm)
3. Least count of screw gauge
Pitch of screw gauge =0.01
Total no of division on the circular scale =
LC of screw gauge = Pitch /No of the circular scale
Zero error (e) =(0)
Zero connection =(e)=0
Radius of the resistance wire
Main Scale Reading (mm) | Circular Scale Reading | Total Reading (diameter) (mm) | Mean D (mm) | Mean radius (D/2) (mm) |
0 | 43 | 0.43 | 0.42 | 0.21 |
0 | 41 | 0.41 |
The connection should be neat, clean & tight.
Source of error
Plug may not be clean
The wire may not be of uniform thickness.
Viva questions
Since the bridge uses one meter long wire, it is called a meter bridge .
It is a point on the wire , keeping jockey at which galvanometer gives 0 deflection .
It is so because the bridge method is a null method (at null point , no current is flowing in galvanometer ) and more sensitive .
Thick Cu strips have negligible resistance over the resistance of alloy meter bridge wire and minimize affect of end resistance .
Circuit diagram
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hiii sir i am sushant raj from cbse i want to help in to my gmail physics pratical ..
Hii myself trisha singh of st thomas school,ranchi of isc board heartly grateful to u for ur best notes of exp related to phy practical.
This is very good notes for intermediate students
standard value of the specific resistance of the material of the given. what?
Thanks guru
So gud notes sir its is so helpful to us
Its very helpful sir
It was very helpful
What is the material of wire used?? Please specify…..
the material of wire used in meter bridge is made of magnanin.
meter bridge experiment discussion ???
The wire should have been of constantun as most of the time it is. But the result doesn’t match. Probably it is because of the experimental errors. It can be possible that he has taken a wire of different material. No need to worry as these problems would vanish once you perform the experiment yourself.
I want to know that when ‘ R’ is in left gap and when R is in right gap
gjb notes good carryon
Thankuu so much. It helped me a lot for my practical experiment..I also recommended this site to my friends.. Wil you plz put up some questions of physics Sec -B expermt Nd full experiment also .
Why 4 is not used in the final formula?
It is not 0.21 ×10^-4 m It is 0.21×10^-3 m
***** 5 star
But sir, what about the conclusion for the experiment
Awsome guru thanks for uploading this data it was really healful to me
good day sir pls I need an answer to this:a battery of 1.50v has a terminal p.d of 1.25v when a resistor of 25ohms is joined to it.calculate the current flowing,the internal resistance r and the terminal p.d when a resistor of 10 ohms replaces the 25 ohms resistor. Thanks
Specific resistance obesarvation
Really these notes were very helpful to me actually I was finding correct reading and calculation of practical but I found no sites which has given correct reading of the practical. I really appreciated the work of creator who has created this content in this website.
Must Mari bhot help ho Gai In physics ka practical ma Thanks
This is really helpful, thank you for this great work.
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Experiment - to find resistivity of the material of a given wire using metre-bridge. - all with video answers.
Chapter Questions
In meter bridge experiment, A thin uniform wire $\mathrm{AB}$ of length $1 \mathrm{~m}$ and unknown resistance $\mathrm{x}$ and a resistance of $12 \Omega$ are connected. In the above question, after appropriate conditions are made, it is found that no deflection takes places in the galvanometer when the sliding jockey touches the wire at a distance of $60 \mathrm{~cm}$ from $\mathrm{A}$. What is the value of the resistance $\mathrm{X}$ ? (A) $18 \Omega$ (B) $8 \Omega$ (C) $16 \Omega$ (D) $4 \Omega$
A thin uniform wire $\mathrm{AB}$ of length $1 \mathrm{~m}$, an unknown resistance $\mathrm{X}$ and a resistance of $12 \Omega$ are connected by thick conducting strips as shown in figure. A battery and a galvanometer (with a sliding jockey connected to it) are also available. Connections are to measure the unknown resistance $\mathrm{X}$ using the principle of Wheatstone bridge. The appropriate connections are. (E Is the balance point for Wheatstone bridge) (A) battery across $E B$ and galvanometer across $B C$ (B) battery across $\mathrm{EC}$ and galvanometer across $\mathrm{BD}$ (C) battery across $\mathrm{BD}$ and galvanometer across $\mathrm{EC}$ (D) battery across $\mathrm{BC}$ and galvanometer across $\mathrm{CD}$
A wire is in the form of a tetrahedron shown in figure. The resistance of each wire is $\mathrm{R}$. What is the resistance of the frame between the corners $\mathrm{A}$ and $\mathrm{B}$. (A) $(2 \mathrm{R} / 3)$ (B) $2 \mathrm{R}$ (C) $\mathrm{R}$ (D) $(\mathrm{R} / 2)$
For the electrical circuit shown in the figure, the potential difference across the resistor of $400 \Omega$ as will be measured by the voltmeter $\mathrm{V}$ of resistance 400 is $\ldots \ldots \ldots$ (A) $(10 / 3) \mathrm{V}$ (B) $4 \mathrm{~V}$ (C) $(20 / 3) \mathrm{V}$ (D) $5 \mathrm{~V}$
In a simple meter-bridge circuit, the both gaps are bridge by coils $\mathrm{P}$ and $\mathrm{Q}$ having the smaller resistance. A balance is obtained when the jockey key makes contact at a point of the bridge wire $40 \mathrm{~cm}$ from the $\mathrm{P}$ end. On shunting the coil $\mathrm{Q}$ with a resistance of $50 \Omega$ the balance point is moved through $10 \mathrm{~cm}$. What are the resistance of $\mathrm{P}$ and $\mathrm{Q}$ ? (A) $[(100) / 3] \Omega,[(100) / 2] \Omega$ respectively (B) $[(50) / 3] \Omega,[(50) / 2] \Omega$ respectively (C) $[(25) / 3] \Omega,[(25) / 2] \Omega$ respectively (D) $[(75) / 3] \Omega,[(75) / 2] \Omega$ respectively
What is the resistance of an open key? (A) $\infty$ (B) Can't be determined (C) 0 (D) depends on the other resistance in the circuit
What is the unit of temperature coefficient of resistance? (A) $\Omega^{-1}{ }^{\circ} \mathrm{C}$ (B) $\Omega^{1}{ }^{\circ} \mathrm{C}^{-1}$ (C) ${ }^{\circ} \mathrm{C}^{-1}$ (D) $\Omega^{0}{ }^{\circ} \mathrm{C}^{-1}$
To verify the laws of combination (parallel) of resistances using a metre bridge
1. 2 different resistances (carbon or wire-wound resistors), 2. metre bridge, 3. galvanometer, 4. a cell or battery eliminator, 5. a jockey, 6. a rheostat, 7. a resistance box, 8. a plug key, 9. sandpaper and 10. thick connecting wires.
Consider two resistances, r1 and r2, are connected in series.
The series combination resistance RS is given by RS = r1 + r2
When connected in parallel, the resistance of the combination is given by Rp
Resistance connected in Parallel
Resistances r1 and r2 connected in parallel to one arm of a metre bridge
sl.no | Resistance R (ohm) | Resistance from the resistance box R (ohm) | Length AD=l | Length DC=100-1 | Rp=100-1/l | Mean resistance (ohm) | |
R1 only | 1 2 3 4 5 | r1 = | |||||
r2 only | 1 2 3 4 5 | r2 = | |||||
r1 and r2 in parallel | 1 2 3 4 5 | Rp = |
1. List the factors affecting the resistance?
ANS: The factors affecting the resistance are,
2. What is the mathematical form of Ohm’s law?
3. What is resistance?
ANS: The ratio of potential difference V across the ends of a conductor to the current I flowing through it. It is represented by R and is given by R=V/I
4. What is ohmic resistance?
ANS: The resistance which obeys ohms law is known as Ohmic resistance.
5. Give examples of non-ohmic resistance?
ANS: Transistors, vacuum tube diodes and semiconductor diodes.
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Every other day, science presents us with one or more ways to feel amazed. There are a host of experiments that show both how we can use things and make newer things out of them. Experiments related to Wheatstone Bridge and the potentiometer are among few such things in science that invoke a curious sense of amazement. Let us study more about the concept of Wheatstone bridge and meter bridge, along with potentiometer.
The concept of wheatstone bridge.
Defined simply, a Wheatstone Bridge is an electric circuit that is used to measure the electrical resistance of a circuit. The circuit is set out by balancing two legs of a bridge circuit. Out of the two, one of the legs is an unknown component which was invented by Samuel Hunter Christie in the year 1833 and later, it improved and popularized by Sir Charles Wheatstone in the year 1843.
Nowadays, technological progress has allowed us to make various measurements through sophisticated tools and machines. However, even today, the wheat bridge remains an authentic way to measure electric resistance, down to the closest milliohms as well.
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The usual arrangement of the Wheat stone bridge circuit has four arms. The bridge circuit where the arms are situated consist of electrical resistance. Out of these resistances, P and Q are the fixed electrical resistances and these two arms are the ratio arms. Next, A Galvanometer connects between the terminals B and D through a switch K 2 . The source of voltage of this arrangement is connected to the terminals A and C through a switch, K 1 .
A variable resistor S is connected between point C and D. The potential at point D is altered by adjusting the value of a variable resistor. If a variation in the electrical resistance value of arm CD is brought, the value of current I2 will also vary as the voltage across both A and C is fixed.
If we continue to adjust the variable resistance, a situation may come when the voltage drops across the resistor S that is I2. Here, S becomes exactly equal to the voltage drop across resistor Q that is I1. Q. So, the potential at point B becomes equal to the potential at point D hence the potential difference between these two points is zero hence current through galvanometer is nil. The deflection in the galvanometer is nil when the switch K2 is closed.
How is the meter bridge experiment carried out using the wheatstone principle.
The meter bridge experiment uses the wheat bridge experiment to demonstrate the resistance of an unknown conductor or to make a comparison between two unknown resistors. Through the above-stated equation, one can easily decipher the specific resistance of a given material
Conclusions of the wheat stone bridge principle are:
According to the Wheatstone-bridge principle, the resistance of length AB/resistance of length BC = R / X
Let l be the length of wire between A and B and then (100 – l) is the length of wire between B and C. Here, P = ρl / A. Since the wire has a uniform cross-section and ρ is constant. Its resistance is proportional to the length. That is P ∝ l, and Q ∝ (100–l). So,
L / (100–l) = R / X
This is how to draw the values of X for different values of R and the mean value gives the value of unknown resistance X.
A potentiometer is an electric device which is used to regulate EMF and internal resistance of a given cell . This helps in providing a variable resistance and therefore, a variable potential difference arising between two points in an electric circuit. It is basically a three-terminal resistor device with an adjustable arm that increases or reduces the resistance in the loop.
Potentiometer (Source: Wikipedia)
Question: Describe how a potentiometer works in an arrangement.
Answer: A potentiometer consists of a uniform wire AB of manganin or constantan that has a length of usually 10 m. it is kept stretched between copper stripes that are fixed on a wooden board by the side of a metre scale. The wire is then divided into ten segments each of 1 m length.
These segments join in series through metal strips between points A and B. A steady current is maintained in the wire AB by a constant source of EMF Eo, called driver cell, that connects between A and B through a rheostat. A jockey slides over the potentiometer wire which makes contact with the wire and cell.
Potentiometer (Source: Wikimedia)
Thus we can say that the potential difference across any portion of the potential of the potentiometer wire is directly proportional to the length of that portion provided the current is uniform.
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IMAGES
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COMMENTS
A metre bridge, also known as a slide wire bridge, is an instrument that works on the principle of Wheatstone bridge. It is used to determine the unknown resistance of a conductor. Below is an experiment on how to find the resistance of a given wire using a metre bridge and to determine the resistivity of its material.
This video channel is developed by Amrita University's CREATEhttp://www.amrita.edu/create For more Information @http://amrita.olabs.co.in/?sub=1&brch=6&sim=...
A Meter bridge is used to calculate resistance values with high accuracy. They work on the principle of a balanced Wheatstone bridge. Khan Academy is a nonpr...
Meter Bridge works on the principle of Wheatstone Bridge. The former is an actual physical lab apparatus while the latter is an electrical circuit. Your meter bridge experiment readings for both the resistance of the unknown wire (S) and length of the wire (l) are computed as the mean values. The meter bridge is also referred to as the slide ...
A meter bridge is an electrical apparatus using which we can measure the value of unknown resistance. It is made using a metre long wire of uniform cross-section. This wire is either nichrome or manganin or constantan. The principle of working of a meter bridge is the same as the principle of a Wheatstone bridge.
Hence law of resistances in parallel i.e. R s = r 1 r 2 /r 1 +r 2 is verified. Precautions: The connections should be neat, clean & tight. Move the jockey gently over the wire & don't rub it. All plugs in resistant box should be tight. Sources of Error: The plugs may not be clean. The instrument screws maybe loose. To verify the laws of ...
This video covers the meter bridge experiment to determine the resistance of an unknown resistor.===== Thanks for WatchingPlease leav...
The Wheatstone bridge can still be used in measuring light values of resistances around the range of milli-Ohms. How Is a Meter Bridge Used in Finding the Unknown Resistance? A meter bridge is an apparatus used to find the unknown resistance of a coil. The below figure is the diagram of a useful meter bridge instrument.
Numerical Examples. Example 1. In a metre bridge experiment, a null point is obtained at a length of 39.8 cm when a 2 Ω resistance is placed in the left gap and a 3 Ω resistance in the right gap. If the two resistances are interchanged, the null point is obtained at 60.8 cm. Calculate the end errors of the bridge.
The unknown resistance can be calculated as: X = R l (100−l) X = R l (100 − l) Then the specific resistance of the material of the wire is calculated as: ρ = πr2X L ρ = π r 2 X L. Where, L is the length of the wire. r is the radius of the wire. More Information: Wheatstone's Bridge. Test Series.
Meter Bridge Experiment using Wheatstone Bridge Principle. Meter bridge is based on the principle of wheat stone bridge and it is used to find the resistance of an unknown conductor or to compare two unknown resistance. The practical diagram is shown in the below figure. where r = radius of the wire and l = length of wire. Task of the Experiment.
Experiment No.2 METRE BRIDGE - 1 AIM:-To find the resistance of the given wire using meter bridge and hence determine the specific resistance of its material. APPARATUS: A meter bridge, galvanometer, one way key, a resistance box, a battery jockey, unknown resistance wire about 1 meter long, screw gauge and connecting wires. THEORY:
where R is the resistance from the resistance box in the left gap, and l is the length of the meter bridge wire from zero ends up to the balance point. (ii) When two resistors r 1 and r 2 are connected in series, their combined resistance is given as follows:. R s = r 1 + r 2. Procedure. Mark the two resistance coils as r 1 and r 2.; To find the value of r 1 and r 2, follow the same steps as ...
About Simulation. In this simulation, you will correlate the principle of Wheatstone bridge with the meter bridge experiment for physics practical class 12. You will learn the theory behind Wheatstone's meter bridge and examine the resistance of a wire. You will determine the resistivity (specific resistance) of a given material of the wire.
Metre bridge is one form of Wheatstone's bridge. Metre bridge consists of thick strips of copper, of negligible resistance, fixed to a wooden board. There ar...
Aim - To find the resistance of a given wire using meter bridge and hence determine resistivity of its material .. Apparatus. A meter bridge (slide wire bridge ) , a lecranche cell, a galvanometer , a resistor , a jockey , a one way key , a resistance wire , a screw gauge , a meter scale , a set of square , connecting wire , a piece of sand paper .
In meter bridge experiment, A thin uniform wire $\mathrm{AB}$ of length $1 \mathrm{~m}$ and unknown resistance $\mathrm{x}$ and a resistance of $12 \Omega$ are connected. In the above question, after appropriate conditions are made, it is found that no deflection takes places in the galvanometer when the sliding jockey touches the wire at a ...
Remove some plug (s) from the resistance box to get the suitable value of resistance R. Get a null point D on the metre bridge wire by sliding the jockey between ends A and C. Note the value of the resistance R and lengths AD and DC. Calculate the experimental value of the equivalent parallel resistance. Repeat the experiment for four more ...
welcome to visual learningMeter bridge || Full explanation with animation || Current Electricity || Physics || 12th classA meter bridge is a simple device us...
The meter bridge experiment uses the wheat bridge experiment to demonstrate the resistance of an unknown conductor or to make a comparison between two unknown resistors. Through the above-stated equation, one can easily decipher the specific resistance of a given material. Conclusions of the wheat stone bridge principle are:
In this video we will perform an experiment based on meter bridge. "To determine unknown resistance by using Meter Bridge apparatus "#meterbridge#meterbridge...
This is the length of the meter bridge that serves as a balancing length. Assume that the distance between locations A and B equals 'l.' Assume that the distance between locations B and C is 'l a,' where l 2 =100 - l 1. Procedure for the Meter Bridge experiment Remove a suitable type of resistance from the resistance box 'R.'
Determination Of Unknown Resistance Using Meter Bridge