Comparison of Mutual inductance using spot galvanometer, introduction about mutual inductance, deflection in spot galvanometer with model readings and youtube links

1. SPOT GALVANOMETER-COMPARISON OF
MUTUAL INDUCTANCE
Associate Professor in Physics
SARAH TUCKER COLLEGE [AUTONOMOUS]
TIRUNELVELI-627007

2. SPOT GALVANOMETER

3. MUTUAL INDUCTION

5. AIM:
To compare the mutual inductance of the given two pairs of coil using spot
galvanometer.
APPARATUS REQUIRED:
A battery, Keys, Resistances, Spot galvanometer, coils, a tap key and Commutator.
FORMULA:
where
M1,M2 – Mutual inductance of the pair of the coil in henry
R1,R2 –Resistances in ohm.
Q1,Q2 – Resistances included in the box Q to get the null
deflection in the spot galvanometer.
COMPARISON OF MUTUAL INDUCTANCE

6. COMPARISON OF MUTUAL INDUCTANCE
K1, K2 - Keys
R.Q - Resistance boxes
SG - Spot Galvanometer
S1, S2 - Secondary Coils
P1, P2 - Primary Coils

7. PROCEDURE
• The primary coils P1and P2 of two pairs of mutual inductance
connected in series to battery and a tap key K. The secondary
coils S1 and S2are connected to the spot galvanometer so that
the coil is induced, current from one coil through the S.G is
opposed to the current in the other coil.
• To check if the connections have been correctly made, K1is
first closed, K2 is open and then press K. The direction of
throw in galvanometer is noted. Now K2 is closed, K1 is
opened and then press K. If the throw is on opposite side then
connections are correct.

8. Procedure…..
• Now both K1,K2 are closed. With a suitable value of resistance
in R, various values are plugged out in Q until, on closing K,
there is no throw in the galvanometer. The values of
resistances in the boxes (R1 and Q1) are noted.
• Now, R1 is increased to R2 and Q1 to Q2 until again, on closing
K, there is no throw in the galvanometer.
• Thus the variable resistance is adjusted to get the null
deflection in the spot galvanometer.

9. P1=500 turns P2=600 turns
S1=400 turns S2=500 turns
R1
in
ohm
Q1
in ohm
R2
in
ohm
Q2
in ohm
Left Right Mean Left Right Mean
300 250 260 255 800 550 552 551 1.689
400 320 330 325 900 600 600 600 1.818
500 370 380 375 1000 660 662 661 1.748
600 432 430 431 1100 730 726 728 1.684
700 510 510 510 1200 760 762 761 1..992
Mean
𝑀1
𝑀2
= 1.786

10. CALCULATION
i) R1 = 300 Ω R2 = 800 Ω
ii) Q1 = 255 Ω Q2 = 561 Ω
𝑀1
𝑀2
=
800 −500
561 −255
𝑀1
𝑀2
= 1.684
𝑀1
𝑀2
=
1.689+1.818+1.748+1.684+1.992
5
𝑀1
𝑀2
= 1.786
Result: The ratio of mutual inductance of
the given pair of coils is
𝑴 𝟏
𝑴 𝟐
= 1.786

11. REFERENCE
Laboratory Manual – III B.Sc. Physics - Non-Electronics
Department of Physics, Sarah Tucker College (Autonomous)
Google Images
PPT’s
 https://www.slideshare.net/saahil750/self-inductance-mutual-inductance-
and-coeffecient-of-coupling
 https://www.slideshare.net/subhalekshmi2013/mutual-induction-39342267
YouTube Links
 https://www.youtube.com/watch?v=Vv2KqqRa3q0
 https://www.youtube.com/watch?v=ZDBfDTEMGaQ