Electromagnetic Induction

Question 1

Faradays Laws of EMI

Answer 1

E= -dδ/dt; 
E= emf generated 
δ= Magnetic flux

Question 2

Magnetic flux δ=?

Answer 2

δ=NB.A
; A=Area
B= Magnetic field
δ= Magnetic Flux

Question 3

State Lenz’s Law

Answer 3

EMF generated opposes change in flux

Question 4

Motional EMF E=?

Answer 4

E= Bvl= Bωl²/2=BAf
; f= frequency
l= length of conductor
ω= angular frequency

Question 5

Induced current I=?

Answer 5

I= I₀ sin ωt

Question 6

Coefficient of self induction δ=?

Answer 6

δ=LI
E=-L dI/dt
; L= coefficient of self induction

Question 7

Self induction L of long solenoid =?

Answer 7

L= μ₀N²A/l= μ₀ n²Αl
; N= No of turns 
n= Turn density 
l=length of coil 
A= Area of cross section of coil

Question 8

Self inductance L of toroid =?

Answer 8

L= μ₀N²A/2πr

; A= Area of cross section of toroid

Question 9

Energy E stored in an inductor =?

Answer 9

E= 1/2 Li^
; L = Inductance
I= Current

Question 10

Coefficient of mutual inductance δ=?

Answer 10

δ=MI
E=-M dI/dt
; M = coefficient of mutual inductance

Question 11

In EMI , coefficient of coupling K=?

Answer 11

K= M/√L1L2
;L1,L2= Mutual inductance of respective coils 
K= coefficient of coupling

Question 12

Mutual inductance M of long coaxial solenoid =?

Answer 12

M= μ₀N1N2A/l
;N1,N2= No of turns on respective solenoids 
l= length of solenoid 
μ₀= permittivity of free space

Question 13

Grouping of coils in series of M=0

Answer 13

L=L1+L2

; L= Self inductance

Question 14

Grouping of coils in series if current in coils is in same direction

Answer 14

L=L1+L2+2M

Question 15

Grouping of coils in series if current is in opposite direction

Answer 15

L=L1+L2-2M

Question 16

Grouping of coils in parallel if current is in same direction in coils

Answer 16

L=L1L2-M^/L1+L2+2M

Question 17

Grouping of coils in parallel if current in coils is in opposite direction

Answer 17

L=L1L2-M^/L1+L2-2M

Question 18

Eddy current i= ?

Answer 18

i= -e/R 
;e= induced emf 
i= eddy current