Now imagine that the coil is subjected to a series of experiments, that we will label 1, 2, etc., for clarity. at the beginning of both experiments 1 and 2, the magnetic field is initially 3.0 t. in experiment 1, the magnetic field is changed in 2.0 ms from 3.0 t to 6.0 t. in experiment 2, the magnetic field is changed in 2.0 ms from 3.0 t to 20.0 t. what is the ratio of the average emf observed in each case, emf1 / emf2?

EMF1/EMF2= 3/17 = 0.176

Explanation:

Experiment 1:

B₁= 3.0 T

B₂= 6.0 T

dt= 2 ms

dB= B₂  - B₁ = 6 T-3 T

dB= 3 T

Now

∅= B*A cosθ  ( A is area of the coil)

d∅= dB*A cosθ

d∅= 3*A cosθ

Average emf

ε₁= d∅/dt

ε₁=3*A cosθ/ 2*10^-3

ε₁=1500*A*cosθ

Experiment 2:

B₁= 3.0 T

B₂= 20.0 T

dt= 2 ms

dB= B₂  - B₁ = 20 T-3 T

dB= 17 T

Now

∅= B*A cosθ  ( A is area of the coil)

d∅= dB*A cosθ

d∅= 17*A cosθ

Average emf

ε₂= d∅/dt

ε₂=17*A cosθ/ 2*10^-3

ε₂=8500*A*cosθ

Ratio of average emf:

EMF1/EMF2= ε₁/ε₂= (1500*A*cosθ)/(8500*A*cosθ)

EMF1/EMF2= 1500/8500

EMF1/EMF2= 3/17 = 0.176

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

hope this ! : )