current sensitivity of a galvanometer

A proton is allowed to fall from rest in it through the same vertical distance h. The time of fall of the electron, in comparison to the time of fall of the proton is, As we know, F = qE = ma⇒ a = qEmh = IqE2mt2t = 2hmqE. The moving coil galvanometer is a highly sensitive instrument due to which it can be used to detect the presence of current in any given circuit. The deflection θ per unit current I is known as current sensitivity θ/I. The current drawn is I. The sensitivity of a galvanometer is higher if the instrument shows larger deflection for a small value of current. If the length of the closed organ pipe is 20 cm, the length of the open organ pipe is, n = NV2l=V2l'(∵ N= 1)According to question,3V4l = V2l'⇒ l' = 4l3 x2 = 2l3 =2 x 203 = 13.33 cm, The electrostatic force between the metal plates of an isolated parallel plate capacitor C having a charge Q and area A, is, Independent of the distance between the plates, Linearly proportional to the distance between the plates, Inversely proportional to the distance between the plates, Proportional to the square root of the distance between the plates, The electrostatic force between the metal plates, For isolated capacitor Q = constantHence, F is Independent of the distance between plates, A metallic rod of mass per unit length 0.5 kg m–1 is lying horizontally on a smooth inclined plane which makes an angle of 30° with the horizontal. It also makes the magnetic field radial so that the angle between the plane of the coil and the magnetic lines of force remains zero at all times during the rotation of the coil. The value of 'n' is, In series grouping equivalent resistance Rseries = nRIn parallel grouping equivalent resistance Rparallel = R/n, I = EnR + R ..... (i)10 I  = ERn+ R ... (ii)Dividing eq. The angle through which the coil is deflected due to the effect of the magnetic torque is proportional to the magnitude of current in the coil. Voltage sensitivity of moving coil galvanometer, Dividing equation (i) and (ii)Resistance of galvanometer, RG = IsVs = 5 x 120 x 10-3 = 500020 = 250 Ω, An inductor 20 mH, a capacitor 100 µF and a resistor 50 Ω are connected in series across a source of emf, V = 10 sin 314 t. The power loss in the circuit is, Power dissipated in an LCR series connected to an a.c source of emf E, P = Ermsirms cosϕ = E2rmsRZ2 = Erms2 RR2+ωL-1Cω2=1022 x 50(50)2 +314 x 20 x 10-3 - 1314 x 100 x 10-62solving we get, P = 0.79 W, The efficiency of an ideal heat engine working between the freezing point and boiling point of water, is, Sink temperature, T2 = 100oC = 100 + 273 = 373 KSource temperature, T1 = 0o C = 0 + 273 = 273 K, %η = 1-T2T1 x 100= 1-273373 x 100 - 100373 x 100 = 26.8%, A thin diamagnetic rod is placed vertically between the poles of an electromagnet. Check you scores at the end of the test. How can this galvanometer be converted into a voltmeter of range 0-12V? 2020 Zigya Technology Labs Pvt. Solution: The cylindrical soft iron core placed inside the galvanometer increases the magnetic field strength, thereby improving the sensitivity of the instrument. Sensitivity is of two types, namely current sensitivity and voltage sensitivity. Your email address will not be published. Then the current drawn from battery becomes 10 I. It is a sensitive electromagnetic device which can measure low currents even of the order of a few microamperes. The voltages across the galvanometer and shunt resistance are equal due to the parallel nature of their connection. The Sensitivity of a Tangent Galvanometer: The sensitivity of the tangent galvanometer is defined as the ratio of the change in deflection of the galvanometer to the current producing this deflection. 2 See answers santy2 santy2 Resistance formulae : R = V/I. A moving coil galvanometer is an instrument which is used to measure electric currents. Suitable shunt resistance is chosen depending on the range of the ammeter. It also the reciprocal of the current sensitivity of a galvanometer. Not easily affected by stray magnetic fields. As the number of turns(length of the coil) is increased to increase the current sensitivity of the device, the resistance of the coil changes. A galvanometer is converted into a voltmeter by connecting it in series with high resistance. The work required to do this comes from, The induced electric field due to the changing magnetic field, The lattice structure of the material of the rod. The general definition of the sensitivity experienced by a moving coil galvanometer is given as the ratio of change in deflection of the galvanometer to the change in current in the coil. When equal and opposite forces F called couple acts on the coil, it produces a torque. d) The magnitude of couple per unit twist k/nAB. It is the ratio of the full-scale deflection current and the number of graduations on the scale of the instrument. Solution: No. Because of this nature, it can detect current in the range of milliamperes. A set of 'n' equal resistors, of value 'R' each, are connected in series to a battery of emf 'E' and internal resistance 'R'. As we know that voltage sensitivity θ/V = (nAB /k)(1/R); the overall value of voltage sensitivity remains unchanged. It can be used only to measure direct currents. f) Torque experienced by a current loop in uniform magnetic field; f) Torque experienced by a current loop in uniform magnetic field; g) Moving coil Galvanometer, its current sensitivity and conversion to Ammeter and Voltmeter. (ii) by (i),10 =(n+1)R1n+1Rsolving we get, n = 10, The fundamental frequency in an open organ pipe is equal to the third harmonic of a closed organ pipe. A galvanometer is converted into an ammeter by connecting it in parallel with a low resistance called shunt resistance. A suitable high resistance is chosen depending on the range of the voltmeter. Q3: What are the Current Sensitivity and Voltage Sensitivity of a Galvanometer? When this coil is placed in a uniform radial magnetic field B, the coil experiences a torque τ. Essential properties of the material used for suspension of the coil are conductivity and a low value of the torsional constant. The moving coil galvanometer is made up of a rectangular coil that has many turns and it is usually made of thinly insulated or fine copper wire that is wounded on a metallic frame. Voltage Sensitivity Using Fleming’s left-hand rule we can determine that the forces on AD and BC are in opposite direction to each other. b) the voltage by connecting it in series with high resistance. Hence the rod gains gravitational potential energy. The resistance of the galvanometer is, Current sensitivity of moving coil galvanometer. In turn, the spring S attached to the coil produces a counter torque or restoring torque kθ which results in a steady angular deflection. Solved Question: A moving coil galvanometer of resistance 100Ω is used as an ammeter using a resistance of 0.1Ω. A plane mirror which is attached to the suspension wire, along with a lamp and scale arrangement is used to measure the deflection of the coil. A moving coil galvanometer is a highly sensitive instrument. The other end of the spring is connected to binding screws. Solved Question: A galvanometer coil of 40Ω resistance shows full range deflection for a current of 4mA. © It is worth noting that voltage sensitivity = Current sensitivity/ Resistance of the coil. I = Total current passing through the circuit. Therefore under the condition that R remains constant; voltage sensitivity ∝ Current sensitivity. Powered By Arb4Host Network. Let us first consider a single turn ABCD of the rectangular coil having a length l and breadth b. A galvanometer is a device that is used to detect small electric current or measure its magnitude. A phosphor-bronze strip that is connected to a movable torsion head is used to suspend the coil in a uniform radial magnetic field. However, today the main type of galvanometer type that is used widely is the D’Arsonval/Weston type or the moving coil type. The maximum deflection current in the galvanometer is 100μA. The deflection θ per unit voltage is known as Voltage sensitivity θ/V. A galvanometer is basically a historical name that has been given to a moving coil electric current detector. Zero-point of the scale is at the centre. (IIT-JEE|2005), Solution: It is given that RG =100Ω , Rs= 0.1Ω, IG =100μA, Substituting the given values, we get I= 100.1mA. The energy of current source will be converted into potential energy of the rod. Where : R = the resistance . The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction 0.25 T is acting on it in the vertical direction. Moving-coil galvanometers are mainly divided into two types: A current-carrying coil when placed in an external magnetic field experiences magnetic torque. Sensitivity is of two types, namely current sensitivity and voltage sensitivity. Sensitivity = dθ / di. Solved question: What is the purpose of introducing a cylindrical soft iron core inside the moving coil galvanometer? The resistance of the galvanometer … This torque causes the coil to deflect. Find the current in the circuit, so that the ammeter shows maximum deflection. A carbon resistor of (47 ± 4.7) kΩ is to be marked with rings of different colours for its identification. Substituting the value of F we already know, Torque τ acting on single-loop ABCD of the coil = BIl × b, Hence the torque acting on n turns of the coil is given by. When current IG passes through the galvanometer, the current through the shunt resistance is given by IS = I – IG. i.e., time t∝m as 'q' is the same for electron and proton. R stands for the effective resistance in the circuit. Required fields are marked *, Apple iPhone 12 Pro review, advantages, disadvantages & features, Importance of Anatomical body position, planes & terms of movement, OnePlus Nord N10 5G review, advantages, disadvantages & features, Uses of the concave mirror and the convex mirror in our daily life, Advantages and disadvantages of using robots in our life, Robot teachers uses, advantages and disadvantages, Copyright © Science online 2014. Hence it is understood that the deflection that occurs the galvanometer is directly proportional to the current that flows through it. Last modified September 7, 2019, Your email address will not be published. Sony Xperia XZ2 Compact review, advantages, disadvantages and specifications, Huawei Honor 7C review, advantages, disadvantages and specifications, Newton’s Universal Gravitation Law, Circular Motion & Factors affecting gravitational field intensity, Applications on the pressure at a point (Connected vessels, U-shaped tube & Mercuric barometer), Electromagnet, Electric generator (Dynamo) uses, structure and types, Vps Web Hosting (Virtual Private Server) advantages and disadvantages. By what factor does the voltage sensitivity change? Develops errors due to factors like aging of the instrument, permanent magnets and damage of spring due to mechanical stress. Current Sensitivity ; The deflection θ per unit current I is known as current sensitivity θ/I. We know that torque τ = force x perpendicular distance between the forces. Thus the sensitivity of tangent galvanometer can be increased by . The galvanometer sensitivity. The quantity nAB / k is a constant for a given galvanometer. Since its discovery in the 1800s, galvanometer has seen many iterations. The magnetic torque thus produced causes the coil to rotate, and the phosphor bronze strip twists. This is because the resistance of the coil is dependent on factors like the length and area of the coil. The pointer deflects to the left or right depending on the direction of the current. The deflection or twist θ is measured as the value indicated on a scale by a pointer which is connected to the suspension wire. Yes or no? Justify your answer. If a galvanometer is a connected in a Wheatstone’s bridge circuit, pointer in the galvanometer shows null deflection, i.e no current flows through the device.

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