What is Galvanometer: Definition and 56 Discussions

A galvanometer is an electromechanical measuring instrument for electric current. Early galvanometers were uncalibrated, but improved versions, called ammeters, were calibrated and could measure the flow of current more precisely.
A galvanometer works by deflecting a pointer in response to an electric current flowing through a coil in a constant magnetic field. Galvanometers can be thought of as a kind of actuator.
Galvanometers came from the observation, first noted by Hans Christian Ørsted in 1820, that a magnetic compass's needle deflects when near a wire having electric current. They were the first instruments used to detect and measure small amounts of current. André-Marie Ampère, who gave mathematical expression to Ørsted's discovery, named the instrument after the Italian electricity researcher Luigi Galvani, who in 1791 discovered the principle of the frog galvanoscope – that electric current would make the legs of a dead frog jerk.
Galvanometers have been essential for the development of science and technology in many fields. For example, in the 1800s they enabled long-range communication through submarine cables, such as the earliest transatlantic telegraph cables, and were essential to discovering the electrical activity of the heart and brain, by their fine measurements of current.
Galvanometers have also been used as the display components of other kinds of analog meters (e.g., light meters and VU meters), capturing the outputs of these meters' sensors. Today, the main type of galvanometer still in use is the D'Arsonval/Weston type.

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  1. S

    Shape of graph of torque vs angular displacement of galvanometer

    I know the torque will be zero when the deflection is zero and will be maximum when the angular displacement is θ0 but how to determine the exact shape of the graph? Thanks
  2. S

    Graph of torque against displacement of galvanometer needle

    My guess is (c) since the rest of the options do not make sense to me but I am not sure about the shape of the graph. Is (c) the correct answer? If yes, how to know whether the shape will be like in the option (straight line then curve downwards) or other shape like straight line only (like y =...
  3. P

    Changing galvanometer reading in the secondary coil of a transformer?

    The present setup is a step-down transformer. Im thinking if n1 is decreased to match or be less than n2, then it will be a step up transformer. so A. (but answers say B)?
  4. jaumzaum

    The REAL difference between a Galvanometer and an Ammeter

    Hello guys. I'm having some trouble to understand the real difference from the Galvanometer and the Ammeter. The best comment I saw in some forum was: Ammeter: ANY instrument used to measure electrical current Voltimeter: ANY instrument used to measure voltage difference Galvanometer: a...
  5. B

    Working out the shunt resistance for a galvanometer circuit

    Here is the problem I have tried to draw the set up for both cases which the question had described above, and came to these 2 equations. But I can't see how it would help me to work out the resistance of the shunt? Any help would be really great! Thanks
  6. N

    Finding the Earth's magnetic field strength using a Galvanometer

    Homework Statement [/B] I am working on a experiment on finding the Earth's magnetic field strength in Denmark. Using a Galvanometer and a constant power source of 5.1V and slowly adjusting the resistance, I was able to find the changes in angle in relation to the changes of current. 2...
  7. P

    What is the effect of a shunt on the sensitivity of a moving coil galvanometer?

    Homework Statement If a shunt of 1/10th of the coil resistance is applied to a moving coil galvanometer,then it's sensitivity becomes (a)10 fold (b)11 fold (c)1/10 fold (d)1/11 foldHomework Equations ϕ / I = NAB/LThe Attempt at a Solution [/B] So sensitivity gets increased by only these...
  8. A

    A Galvanometer of Coil Resistance 50 Ω Deflects Full Scale....

    Homework Statement A galvanometer of coil resistance 50.0 Ω deflects full scale for a current of 3.50 mA. What series resistance should be used with this galvanometer to construct a voltmeter which deflects full scale for 35.0 V Homework Equations /Known Variables[/B] R1 + R2... + Rn = Rtotal...
  9. Muthumanimaran

    Finding the maximum value of current

    Homework Statement galvanometer with 50 divisions on the scale requires a current sensitivity of 0.1 m A/division. The resistance of the galvanometer is 40Ω. If a shunt resistance 0.1 Ω is connected across it, find the maximum value of the current that can be measured using this ammeter...
  10. Asmaa Mohammad

    Factors determining the sensitivity of a galvanometer

    Homework Statement A galvanometer is connected to a solenoid, and there is a magnet bar entering the solenoid to induce an emf. What factors determine the displacement of the pointer of the galvanometer? Homework Equations emf (induced) = -N ΔΦ/ Δt sensitivity of the galvanometer = θ/i The...
  11. Asmaa Mohammad

    The sensitivity of the galvanometer

    Homework Statement Homework Equations sensitivity= θ/i The Attempt at a Solution That's the answer in my textbook: Sensitivity = θ/i = 60/30 = 2 deg/mA But I wonder why it used the angle 60 (the angle between the coil face and the field lines) instead of the angle 30 (the angle between the...
  12. S

    Value of resistor for full scale deflection with 10A

    Homework Statement In order to provide full scale deflection the coil current required in a galvanometer is 190μA and the resistance of the coil in the galvanometer is 35Ω - What is the value of the resistor to be connected in parallel with the meter so that full scale deflection is obtained...
  13. moenste

    Rate of change of current with time, galvanometer deflection

    Homework Statement (a) What is meant by the statement that a solenoid has an inductance of 2.0 H? A 2.0 H solenoid is connected in series with a resistor, so that the total resistance is 0.50 Ω, to a 2.0 V DC supply. Sketh the graph of current against time when the crrent is switched on. What...
  14. moenste

    Two moving-coil galvanometers

    Homework Statement (a) A moving-coil galvanometer consists of a rectangular coil of N turns each of area A suspended in a radial magnetic field of flux density B. Derive an expression for the torque on the coil when a current I passes through it. (You may assume the expression for the force on...
  15. moenste

    Moving-coil galvanometer graph

    Homework Statement A square coil of side a and consisting of N turns is free to rotate about a vertical axis through the mid-points of two opposite sides. It is situated in a uniform horizontal magnetic field of flux density B so that the plane of the coil makes an angle θ with the field. Draw...
  16. PratyashAstro

    How Do You Measure Absolute Capacitance with a Ballistic Galvanometer?

    My question is : What is the absolute capacitance?In my electricity lab, I was assigned to prepare a report on measuring absolute capacitance of a capacitor using ballistic galvanometer. I am familiar to the term self capacitance but not the absolute one. My mentor asked me to find it out by...
  17. R

    A confusion with tangent galvanometer

    When no current is passed through the coil it shows no deflection i.e. B is in the direction shown. But according to theory both fields should be perpendicular (Earth's horizontal field and the one due to coil). But I am confused because the coil would ideally create a magnetic field that is...
  18. A

    Experimental physics i am very frustrated -- convert galvanometer into an ammeter

    I am trying to convert galvanometer into an ammeter. But after finding Galvanometer resistance and shunt values, and cut a wire according to that thickness and connected. But still, the galavanometer reading is not similar to that of the standard ammeter reading connected in the circuit. Any one...
  19. gracy

    Potentiometer and galvanometer experiment

    Homework Statement Zero deflection in galvanometer Homework Equations If potential difference across between two points between which galvanometer is kept is zero galvanometer shows zero deflection. The Attempt at a Solution But my doubt starts from this video at 3:33 to 3:44 teacher says...
  20. W

    Achieving the Balance Point: Current Flow & Galvanometer Reading

    Homework Statement when the balance point is achieved , there're no current passing thru , so Galvanometer should show 0 . Am i right... so there's no current passing thru the 20 ohm resistor . so my working is ( 8.1/120 )(40) = 2.7 V ... correct me if I'm wrong...Homework EquationsThe Attempt...
  21. M

    How Do You Calculate the Series Resistance for a Voltmeter Using a Galvanometer?

    A galvanometer of coil resistance 50 Ω deflects full scale for a current of 3.50mA. What series resistance should be used with this galvanometer to construct a voltmeter which deflects full scale for 35.0 V ? r=50 Ω I=3.50mA=0.0035 V=35.0v R=? I= V/R The Attempt at a...
  22. Hardik Batra

    How is a Galvanometer Converted into an Ammeter Using a Shunt?

    To make ammeter, Resistance of proper small value is joined in parallel to the coil of galvanometer.This resistance is called a shunt. For smaller resistance value, We can not use the smallest resistance wire that is directly wound on coil of galvanometer so the resistance will become...
  23. A

    Displacement current and galvanometer

    Dear All, I have a doubt whether galvanometer detects displacement currents due to time varying electric field or not?please let me know,if anybody have an idea about this. Regards Arvind
  24. Entanglement

    Galvanometer Frame: Aluminum Advantages

    Why is the frame in galvanometers made if aluminum ??
  25. Z

    Converting Galvanometer to Ammeter: Resistance Wire Placement

    Homework Statement how will you convert a galvanometer of resistance 150 ohm giving a full scale deflection for a current of 3 milli ampere to a ammeter of range 0 to 6 ampere?a uniform rsistance wire of length 60cm and 2 ohm is given.find the length of the wire required? Homework...
  26. S

    What factors contribute to the deflection of a galvanometer?

    In a galvanometer the magnetic poles are cut in such a fashion which ensures radial magnetic field. If field is radial then the angle between magnetic moment i.e Area vector of the coil and field is zero. Thus the coil should not experience any torque when current is passed through the coil...
  27. A

    Converting a galvanometer to ammeter and voltmeter.

    How will you convert a galvanometer of resistance 12 ohms showing full scale deflection for a current of 3 milli ampere to (i) Ammeter of range o to 6 Ampere (ii) Voltmeter of range 0 to 18V.
  28. S

    (D'arsonval galvanometer) moving coil meter

    Hello, just been reading a little bit about the basics of moving coil meter and one thing is bugging me. First if we have a basic square looped coil in and uniform magnetic field. There is torque ( m x B ) due to the magnetic field and then there is the system/spring attached to the coil...
  29. P

    Direction of deflection in a galvanometer?

    In which direction will the pointer move when current is passed? ------->-------(|)--------->---------- [Galvanometer] Does it move to the right? AND There is another one that is connected from top to bottom: | | ^ | | | (|) [Galvanometer] | | | ^ | | | Where will the (|) move?
  30. I

    Conversion of Galvanometer to Ammeter

    This is kind of a stupid question but...to measure high currents, a galvanometer is connected parallel to a shunt resistance so that most of the current passes through the shunt resistance but only a small amount of current passes through the galvanometer. But wouldn't this defeat the purpose of...
  31. M

    Galvanometer, voltage drop readings

    i have problem to conceptualize this old galvanometer readings for voltage drop. i plot a diagram of circuit of interest for bether explanation of what's bothering me. so, in DC circuit with some resistor in series, electric current is constant and is of some known value. and if i want to use...
  32. D

    How to Calculate Shunt Resistance for Converting a Galvanometer to an Ammeter?

    A galvanometer has a full scale current of 0.100 mA and a coil resistance of 50ohmes. In constructing an ammeter of 60mA full scale, what shunt resistnace is needed?I'm lost on this one.
  33. D

    Galvanometer to ammeter/voltmeter

    Homework Statement The resistance of a galvanometer coil is 25ohms and the current required for full scale deflection is 500μA. a) explain how to convert the galvanometer to an ammeter reading 20mA full scale, and compute the shunt resistance b) explain how to convert the galvanometer to a...
  34. L

    Finding the Null Point with a Galvanometer: Advice Needed

    I have set up an apparatus to find the Null point with a galvanometer. I am unable to find one as the galvanometer always points to the right, no matter what. Help anyone?
  35. M

    How Does a Moving-Coil Galvanometer Measure High Voltages and Currents?

    Homework Statement a moving-coil gavanometer consists of a coil that is free to rotate between the poles of a permanent magnet. the magnetic field strength between the poles is 5 x (10^-2) T. The coil consists of 250 loops of copper wire, diameter 0.5 mm, wound to form a square coil, with an...
  36. Z

    Conversion of a Galvanometer to an Ammeter

    I had this doubt for over 1 year! I thought of asking about it here. In the conversion of a galvanometer to an ammeter by connecting a shunt in parallel to the galvanometer, maximum amount of current flows through the shunt because it has a very very low resistance. In other words, very less...
  37. B

    Who made the D'Arsonval/Weston galvanometer movement?

    hey I've been snooping around trying to find out who invented the D'Arsonval/Weston galvanometer movement? I am not able to find it or in other words I am getting different sources from different web?.. so who invented the D'Arsonval/Weston galvanometer movement.?
  38. L

    Regarding current sensitivity of galvanometer

    Homework Statement a galvanometer with 50 divisions on the scale requires a current sensitivity of 0.1 m A/division. find the galvanometer current? Homework Equations IS= \theta/I TO find the galvanometer current, i multiplied 50 with 0.1 to get the galvanometer current, as instructed...
  39. A

    Tangent Galvanometer help (square loops around compass)

    What I had to do for a physics prac was to create a tangent galvanometer using this like...square piece of wood and a flat piece of wood in the middle... and we put a compass in the middle and increased the number of coils (carrying current) and recorded the deflection made by the compass and...
  40. P

    Small/Cheap Galvanometer Needed

    Hello, I'm doing an experiment and need a small and cheap galvanometer. Does anyone know where can I find it? Regards
  41. H

    Testing the Magnetism of a Solenoid & Galvanometer

    suppose you have a solenoid with hollow core connected to a galvanometer. On one side you have a S-N magnet (ie. the N pole is nearer to the solenoid). On the other side you have a N-S magnet( ie. S pole is nearer to solenoid). ie. [S - N] [Solenoid] [N - S] Both magnets are...
  42. A

    Why do we convert a galvanometer into voltmeter and ammeter?

    why we convert a galvanometer into voltmeter and ammeter?
  43. I

    Direct Current Circuit with Galvanometer.

    [SOLVED] Direct Current Circuit with Galvanometer. Homework Statement http://img299.imageshack.us/img299/6357/document002aa5.jpg Homework Equations V = IR The Attempt at a Solution http://img263.imageshack.us/img263/6684/document003kl5.jpg I did the following but the...
  44. G

    Galvanometer has a coil with a resistance

    part 1: A galvanometer has a coil with a resistance of 81 W. A current of 131 mA causes full scale deflection. Calculate the value of the series resistor that is required in order to use the galvanometer as a Voltmeter with 40 V full scale. so to make a voltmeter, the galvanometer and...
  45. Amith2006

    Sensitivity of a galvanometer

    Homework Statement 1) A capacitor of capacity 3 micro farad charged by a potential of 2 volt when discharged through a Ballistic galvanometer gives a deflection of 24 divisions. Determine the sensitivity of the Ballistic galvanometer. Homework Equations The Attempt at a Solution...
  46. T

    Build a Galvanometer for Laser Pattern Creation

    hey all, ill start you off with what I am trying to make here... I am tryting to make a galvanometer.. 2D. I am trying to make a galvanometer so i can bounce a laser off a mirror mounted on it. then use the mirror to create laser patterns. first of all, does anybody know where i...
  47. P

    Galvanometer to Voltmeter Question

    A galvanometer of coil resistance 50 ohms deflects full scale for a current of 3.5 mA. What series resistance should be used with this galvanometer to construct a voltmeter which deflects full scale for 35 Volts?
  48. L

    Using Galvanometer of 90 Ohms Resistance for 150V Voltmeter & 10A Ammeter

    A galvanometer of 90 ohms internal resistance has a full-scale current of 350. microA. Describe how to use this meter to make : (a) a 150 V voltmeter, and (b) a 10.0A ammeter So (a) Resistors must be connected in series with the galvanometer, R=4.29 x 10^5 ohms. (b) A shunt resistor must...
  49. E

    Measuring wire tension with a galvanometer

    Hello all. I would like to measure the tension on a very thin magnet wire and I have read about people making scales with a galvanometer (voltmeter). Basically, instead of using the meter to measure current, you send current thru the galvanometer and use the needle to exert force on an object...
  50. P

    R: How does a Moving-Coil Galvanometer Indicate Current Strength?

    I know that the pointer of the galvanometer makes use of the turning effect to indicate the strength of the current. Say, the pointer is moved to the position of 8mA, if the current is suddenly withdrawn, the pointer would be pointing back to zero. What's the mechanism behind this?
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