Conversion of Galvanometer into Ammeter

• Important conversion of galvanometer into ammeter pdf for Intermediate students.
• APPARATUS: A moving coil galvanometer (Weston type), high resistance box (H.R.B), voltmeter, ammeter of 1.0 amp range, fractional resistance box (F.R.B), rheostat, two plug keys, screw gauge, battery (2-3 cells), sand paper and connecting wires, shunt wire (copper).
• Important conversion of galvanometer into ammeter practical observations for Intermediate students.
• Diagram 
• PROCEDURE: I drew circuit diagram and made tight connections according to diagram. I connected H.R.B, battery, key K₁ and galvanometer in series which forms a loop.
• Important conversion of galvanometer into ammeter experiment for Intermediate students.
• Then I connected. F.R.B along with K, in parallel to galvanometer. I closed K, and opened K₂. I plug out suitable resistance from H.R.B and obtained even number deflection on galvanometer. Now I also closed K, and observed that deflection on galvanometer becomes zero. Then I plug out shunt resistance S from F.R.B which makes deflection on galvanometer half. I calculated resistance of galvanometer by formula   G= RS/R-S
• Important conversion of galvanometer into ammeter class 12 for Intermediate students.
• I took two more observations by changing values of R by same method. I calculated mean value of resistance of galvanometer. Then I noted the emf of cell using a voltmeter and calculated current passing through the galvanometer with resistance R by formula
• Important conversion of galvanometer into ammeter practical observations table for Intermediate students.
• I = E/R+G  I calculated the current required for full scale deflection by
• Where n is the total number of divisions in galvanometer scale. Then in order to convert galvanometer into ammeter i calculated shunt resistance by formula.
• Important convert galvanometer into ammeter experiment for Intermediate students.
• Then I took a copper wire and used it as shunt resistance and measured its diameter at different points using screw gauge and calculated mean diameter and radius (r). Then I calculated length I of the wire by formula
• I connected this length of wire in parallel to the galvanometer and this arrangement worked as converted ammeter.
• Important experiment to convert galvanometer into ammeter for Intermediate students.
• I connected ammeter in series to galvanometer according to circuit diagram and I took out a suitable resistance from H.R.B and noted the reading on both meters. Then I converted the galvanometer into ammeter and calculated the difference between two readings which came out nil.
• Observations and Calculations: 
• Current for full scale defection (using Ohm's law): Mean value of G = 123.2 Q  E.M.F. of the battery (or cell) with a voltmeter-1.3 volts
• Total number of divisions on the galvanometer scale = n = 30 divs.
• From observation No. 01 (take 1 or 2 or 3),
• Resistance R = 4000 Ohms.
• Deflection = 0=30 divs.
• Current passing through galvanometer = 1 = E RG (Ohm's law)
• Current for full scale deflection (30 div) = 1=xn
• Hence Ex30 1.3 x30 (R+G) (4000+123.2)30 = -3 A=0.315x10 A = 0.315 mA
• Shunt resistance for conversion of galvanometer into an ammeter of range 01.0
• amperes:
• The range of ammeter for conversion i.e. I = 1.0 A
• The shunt resistance = Rs = G 1-1g
• Rs = 0.315x10-3 1-0.315x10-3 123.2 = 0.0388 Ω
• Calculation of length of shunt wire (Copper): Least count of screw gauge = 0.01 mm   Zero correction = zero
• Observed diameter = (i) 0.40 mm (ii) 0.40 mm (iii) 0.40 mm
• Mean diameter = 0.40+0.40+0.40 3 = 0.40 mm
• Radius of the copper wire = r = d/2 = 0.40/2 = 0.20 mm = 0.020 cm
• Specific resistance of copper wire = p = 1.72 x 100-cm
• Length of wire used as shunt = 1 = 3.14x (0.02)2x0.0388 1.72 x 10-6 = 28.33 cm
• Verification: Checking the accuracy of converted galvanometer Total number of divisions of galvanometer = n 30 divs.
• 1.0 So, the value of each division of shunted galvanometer = -0=0.30
• RESULT: It is found that to convert the galvanometer into an ammeter reading up to 1.0 ampere, the galvanometer should be shunted with a resistance of 0.03880.