EMI 2

Question 1

what is motional emf

Answer 1

It is the emf induced in a conductor due to its motion in a the magentic field.

Question 2

what is self induction

Answer 2

self induction is the phenomenon of production of induced emf in a coil, when a change in current passes through it.

It is the property by virtue of which the coil opposes any change in the strength of current through it by inducing an emf.

The emf is called as back emf as it opposes the change in current.

Question 3

what is flux linkage

Answer 3

n this case, flux linkage through a coil of N turns is
proportional to the current through the coil and is expressed as
N ΦB ∝ I
N ΦB = LI
where constant of proportionality L is called self-inductance of the coil. It
is also called the coefficient of self-induction of the coil.

Question 4

define self inductance in terms flux linkage

Answer 4

The self inductance of a coil is numerically equal to the flux linked with it when the current rhough the coil is 1A.

Question 5

what is self inductance in terms of back emf

Answer 5

E= -L ( dI/dt)

The self inductance of the coil is numerically equal to the emf induced in the coil when the rate of change of current is 1 A/s

Question 6

define 1 H in terms of self inductance

Answer 6

1 henry is the self inductance of a coil when the rate of change of current in the coil is 1 A/s, induced an emf of 1V in the coil.

Question 7

Physically, the self-inductance plays the role of inertia. explain

Answer 7

It is the electromagnetic analogue of mass in mechanics.

Self inductance is called the inertia of electricity because it opposes any change of current in the coil.

Question 8

can a wire act as an inductor ? why or hwy not?

Answer 8

A wire cannot act as inductor because the area of cs of a wire is negligible hence magnetic flux linked with the wire is also negligible

The wire should in the form of a coil to act as inductor.

Question 9

factors affecting self inductance

Answer 9

• permeability of the core
• no of turns
• area of corss section
  -length of the coil

Question 10

define mutual inductance

Answer 10

Mutual induction is the phenomenon of production of induced emf in one coil due to change in current in another coil.

Question 11

what is the mutual inductance in terms of flux

Answer 11

The flux in the secondary coil is directly proportional to the flux in 1st coil.

Φ2 α i 1
Φ2 = M i1

M= mutual inductance, coeff of mutual inductance

The mutual inductance is numerically equal ot the magnetic flux linked with the coil, when a unit current passes through the other coil.

Question 12

What is mutual inductance in terms of emf induced

Answer 12

E= M (-di/dt)

Mutual inductance between two coils in the emf induced in the sec. coil when the current changes at the rate of 1 A/s in the prim. coil.

Question 13

define 1 Hnery in terms of mutual inductance

Answer 13

1 henry is the mutual inductance between two coils when the rate of change of current in the prim coil is 1A/s induced an emf of 1V in the sec coil

Question 14

Factors affecting mutual inductance

Answer 14

• no of turns
• common cross sectional area
• dist b/w two coils
• relative orientation of 2 coils

Question 15

relative orientation of 2 coils

Answer 15

i) the flux leakage is minimum when the 2 coils are coaxial. intertwined. Max mutual inductance

ii) the flux leakage is moderate when the 2 coils are placed side by side

ii) the flux leakage is max when the 2 coils are present in such a way their axes are perpendicular. Min mutual inductance

Question 16

what are some applications of self inductance

Answer 16

i) sparking:
- when a circuit is switched off, a self induced emf is set up in the same direction as the original emf, which causes a spark across the circuit.

ii) non inductive windings
- in resistance boxes, different resistance coils have to be used.
- the wires are arranged in such a way that net self inductance is minimal.
- when a wire is wound around an iron core and once again looped back on itself, the self inductance is very low. this is because both the loops would produce an emf in opposite direction which cancels itself.