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Lab 3: EQUIVALENT INDUCTANCE IN SERIES AND PARALLEL COPULING; COUPLING COEFFICIENT 1 | P a g e
OBJECT: 1. Measure equivalent inductance of two coils, for series coupling with aiding current
and opposing current.2. Measure equivalent inductance of two coils, for parallel coupling with aiding
current and opposing current3. Determine Coupling Coefficient ‘k’ as a function of distance and plot it.
3.1 SAFETY NOTES:1. Power off LCR meter while making connections and after performing the lab.2. Carefully handle the apparatus. Do not drop the helmholtz coils or LCR meter down.
3.2 EQUIPMENTS/ REQUIREMENTS:1. A Pair of coils.2. LCR meter3. 1 meter scale.4. Connecting leads with banana connectors
3.3 THEORY:3.3.1 Inductance:According to Faraday’s law, “The induced emf in a circuit is equal to the negative of the rate at which the magnetic flux through the circuit is changing with time.”
(1)
It is an ability of a conductor to induce voltage when the current changes. the smbol for inductance is L and its unit is Henry (H).
(2)
3.3.2 Mutual Induction:When the current in a inductor changes, the varying flux can cut across an other inductor nearby, producing induced voltage in both inductors. This is called Mutual induction. The unit of mutual inductance is also Henry (H).
3.3.3 Coefficient of Coupling:The fraction of total flux from one coil linking another coil is the coefficient of coupling ‘k’ between the coils.
(3)
Applied Physics/Physics Engr.Ramsha Fatima
Lab 3: EQUIVALENT INDUCTANCE IN SERIES AND PARALLEL COPULING; COUPLING COEFFICIENT 2 | P a g e
If k <1 then there is loose coupling between the coils if k has high value than there is tight coupling between them and if k=0 then there is no mutual inductance. In terms of mutual inductance
3.4 REFERENCES:1. ‘Fundamental of Physics’ by Halliday Resnick and Walker.2. ‘Text book of Electrical Technology’ by B.L.Theraja
3.7 EXPERIMENTAL SETUP:
3.8 PROCEDURE:1. Measure the inductance L1 and L2 of both coils.2. Make connections for series coupling with aiding current as shown in figure 3.1.3. Vary distance between coils from a step of 1cm and measure inductance each time.4. Repeat the above procedure for series coupling with opposing current and parallel
coupling with aiding and opposing current.
3.9 OBSERVATIONS: L1 = ________mH, L2 = __________mHFor Series:
Distance 'x'cm
Inductance (mH) Mutual Inductance
m(H)
Coupling Coefficient
'k'aiding
currentopposing current
Applied Physics/Physics Engr.Ramsha Fatima
Lab 3: EQUIVALENT INDUCTANCE IN SERIES AND PARALLEL COPULING; COUPLING COEFFICIENT 3 | P a g e
For Parallel:
Distance 'x'cm
Inductance (mH) Mutual Inductance
m(H)
Coupling Coefficient
'k'aiding
currentopposing current
3.10 GRAPH:Plot graph between coupling coefficient ‘k’ versus distance ‘x’ using your observations.
3.12 RESULT AND DISCUSSION:
Applied Physics/Physics Engr.Ramsha Fatima
