6 em05 moving coil meter and motor
Post on 24-Oct-2014
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EM 5.8
AL PhysicsMoving Coil Galvanometer
Turning torque (by I) = Resisting torque (by hairspring)
AL PhysicsMoving Coil Galvanometer
Concave magnet and small gap Constant Radial field B magnetic force magnetic force coil plane coil plane (always) Constant TorqueConstant Torquei.e.
= BANI sin 90o = BANI
Resisting torque due to the hairspring in which the restoring torque is directly proportional to the angle turned.i.e.
’ = k where k is the torisonal constant (~ force constant) is the angle turned
At Equilibrium, = ’BANI = k = (NBA / k) I
’’
I if N, B, A and c are constant I if N, B, A and c are constant
linear scale !!
EM 5.8
AL PhysicsMoving Coil Galvanometer
Current Sensitivity = / I = deflection per unit current
/ I = NBA / k
In order to increase the current sensitivity,
• no. of turn of coils , but the armature will be too bulky and the size of the air gap cannot be too small.
• Magnetic field in the air gap , i.e. Stronger magnet is used and the air gap should be as narrow as possible.
• area of the coil ,but the coils will swing about its deflected position.
(4) Weaker hairspring,but if the opposition of the suspension is too weak (reading again take time).
EM 5.8
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EM 5.8
AL PhysicsPractical D.C. Motor
Concave magnet
Smoother and Faster
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EXERCISEEXERCISE M.C. # 17, 18
5 minutes
EM 5.8
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EM 5.8
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EM 5.8
AL Physics
EM 5.8
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