6.7E Extra Equations and Graphs for Electromagnetic Induction

Question 1

Equation for magnetic flux density of a solenoid? - we do not have to apply this equation only know it

Answer 1

b = (mew) nI 
where  
b = magnetic flux density 
n = turns of coil 
I = current 
(mew) = constant of value 1.26x10^-6

Question 2

Equation for magnetic flux density of a straight electrical conductor?

Answer 2

B = (mew)I / 2(pi)r 
where 
b = magnetic flux density 
(mew) = constant of value 1.26x10^-6 
r = distance(length)

Question 3

What is the constant mew?

Answer 3

the permeability of material , how easy it is to create a magnetic field within this material

Question 4

What is the graph for change of magnetic flux linkage over time when power supply is ac?

Answer 4

A sine graph

Question 5

What is the graph for change of emf over time when power supply is ac?

Answer 5

An inverse cos graph

Question 6

Why is the answer an inverse cos graph?

Answer 6

Since emf is the rate of change of magnetic flux linkage, hence steepest points mean emf is greatest (which is where linkage = 0) and least steep points are where emf is lowest

Question 7

Why is it inverse / emf is negative initially?

Answer 7

Due to Lenz Law, the emf created will flow in such a way to oppose the change in magnetic flux linkage

Question 8

How does an MRi scanner work?

Answer 8

It is a solenoid supplied with current. This causes a magnetic field which alligns water molecules. Since the power supply is ac the molecules gain energy. When magnetic field is released the molecules return to original places and release this energy as radiation