16,17: EM, EMI

Question 1

Define magnetic field

Answer 1

Magnetic field is the region in which a magnetic material, current carrying conductor or moving charge carries may experience a magnetic force.

Question 2

Definite Magnetic Flux Density/ TESLA/ B

Answer 2

MFD at a point in the magnetic field is defined as the force per unit length exerted on a long straight conductor carrying a unit current placed perpendicular to the magnetic field.

Question 3

Equation for:
1. Force on moving charge
2. Force on current carrying conductor

Answer 3

1. F = Bvq
2. F = BIL

add cos/sin where necessary,the angle is the angle made with the bfield

Question 4

Define Magnetic flux

Answer 4

Magnetic flux through a plane surface is the product of the component of the magnetic flux density normal to the surface and area of surface.

Question 5

Define Magnetic Flux linkage

Answer 5

MFL through a loop is the product of magnetic flux through the loop and the number of turns of wire in the loop

Question 6

State the equations for
1. Magnetic Flux Density, B
2. Magnetic Flux, phi
3. Magnetic Flux Linkage, capital phi

Answer 6

1. B = F/IL
2. phi = BA
3. capital phi = NBA

Question 7

Define Faraday’s law

Answer 7

Faraday’s law states that if there is a change in magnetic flux linkage, there is EMF induced.
EMF is directly proportional to the rate of change of MFL.

Question 8

Define Lenz Law

Answer 8

Lenz Law states that the EMF induced is in the direction such as to oppose the change in the MFL which is inducing it.

Question 9

How to proof:
1. emf = BLv
2. emf = 1/2 x B x r^2 x angular velocity

Answer 9

1a: NBA -> A=Lx > x/t = v
1b: Bqv = qE; E=p.d/L thus emf = BLv

2: Area of circle = 1/2 x r^2 x radians then sub in

Question 10

What happens to emf induced when the period is halved

Answer 10

1. EMF induced halved
2. Period halved