magnetic flux - ch 21

In the mathematical expression for Magnetic flux, BA cosθ, the magnitude of B is the strength of the magnetic field produced by the current in the loop.

false. b is the magnitude of the external magnetic field

In the mathematical expression for Magnetic flux, BA cosθ, θ is the angle between B and A when the vectors are tip to tail.

False. θ is the angle between B and A when the vectors are tail to tail.

anytime vectors multiplied , rule is vectors must be TAIL TO TAIL, tip to tail is when vectors are added.

false, cos90 is zero, flux will have its minimum value of 0

A in Fardays law magnetic equation

area enclosed by the loop (in m²)

the direction of A is what to the surface of the enclosed loop?

always perpendicular to the surface of the enclosed loop

maximum amount of magnetic field (B)

vector in direction of B

magnetic flux dependent on

strength of external magnetic field, size of loops area and orientation of the loop

when B and A are perpendicular

flux is zero

magnetic flux proportional to

number of total lines passing through loop

flux equation (number of loops)

E= voltage/induced emf

N= number of loops , minus sign has to do with direction of the induced emf

delta flux = BAcostheta

• since flux is equal to BAcostheta we can change the magnetic flux 3 diff ways

• 1- change strength of field in loop, B

• 2- change size of loop , A

• 3- change orientation of loop in field, theta.

Lenz’s law

explains the minus sign in Farday’s law

says that direction of induced emf will always oppose change that is proudcing emf

As a bar magnet is pushed into a conducting loop, what element of the magnetic flux is changing?

external magnetic field strength, B- creating a battery like effect , when magnetic is pushed into loop it is increasing towards the floor, taken out it would be decreasing towards ceiling

• it would not be the area, not changing the size of the conducting loop

• it would not be the angle between A and B

faster change of flux

bigger the induced emf

As a loop is rotated in an external magnetic field, what element of the magnetic flux is changing?

angle between A and B

what element of the magnetic flux is changing in this situation?

the area of the loop, A

equation to use during this situation

E= Blv

when bar is sliding across rail

as a loop is ROTATING in an external magnetic field, what element of the magnetic flux is changing?

the angle between A and B