Chapter 6- Magnetic Fields

Question 1

Magnetic field definition

Answer 1

A region in which magnetic materials experience a force

Field can be produced in three dimensions

Question 2

Magnetic fields lines flow from

Answer 2

North to south

Question 3

Neutral point is located

Answer 3

Somewhere between the north and south poles

Will show up experimentally as the compass won’t know which way to point

Question 4

What else produces magnetic fields

Answer 4

Electric currents

Question 5

If current is coming out of the page then the central point will have a….

Answer 5

Circle with a dot inside it

Question 6

If current is going into the page then the central point will look like….

Answer 6

A circle with a cross inside it

Like a screw

Question 7

A spring like coil is called a

Answer 7

Solenoid

Question 8

What equation let’s you measure the strength of a magnetic field

Answer 8

F= B IL

Question 9

What is the strength of a magnetic field called

Answer 9

Called the magnetic flux density

(Symbol of B in BIL

Question 10

For BIL to work the wire…

Answer 10

Carrying the current needs to be perpendicular to the magnetic field

F= BILsin•

Theta(•) is the angle between the wire and the field
Is at its max/ at 1 when perpendicular

Question 11

Unit of magnetic flux density

Answer 11

Tesla (T)

Or NA^-1 m^-1

Question 12

Which rule is helpful to get directions of force field and current

Answer 12

Left hand rule

Force= thumb (forceful finger)
Field= first finger 
Current= third finger (curls to make a 'c')

Question 13

When an electron moves in an electric field we get

Answer 13

Circular motion

Question 14

BIL used for

Answer 14

Current carrying wires

Question 15

BeV used for

Answer 15

Single charges

Question 16

The force that the electron will love when using the LHR must be remembered to take into consideration

Answer 16

The direction of electron is in opposite direction to current flow

Question 17

There is no work done at 90* so electron…

Answer 17

Never loses energy, so remains in the orbit

Question 18

For a current in a wire it is

Answer 18

Getting pushed by magnetic field
Getting repelled by other electrons
Will keep getting pushed until forces are equal
Given the charge difference, there is a potential difference (deficit of electrons)

Question 19

What is the Hall effect

Answer 19

When a potential difference develops in the wire due to a current flowing
Gets pushed by magnetic field
Repelled by other electrons
Will keep getting pushed until forces are equal
There is a deficit in electrons
So there is a charge difference
Creating potential difference around the wire

Question 20

Voltage eq for electric field

Answer 20

E= Vd

Question 21

Magnetic flux density symbol

Answer 21

B

Question 22

Flux is the idea of

Answer 22

Total field lines captured within an area

Question 23

To get an increase in flux

Answer 23

Increase area

Increase magnetic flux density

Question 24

Flux symbol

Answer 24

Phi

Question 25

Flux unit

Answer 25

Measured in Weber Wb Tm^2

Question 26

Won't capture anything if not in

Answer 26

Perpendicular circumstances

Question 27

Faraday's law

Answer 27

Emf= the rate of change in flux

Question 28

A change in flux causes

Answer 28

A current to be induced

Question 29

Lenz's law

Answer 29

The induced magnetic field will always oppose the change in magnetic flux that is causing it (Why there is a negative sign in front of eq)

Question 30

Equation where Lenz's law is seen

Answer 30

Emf= -N x rate of change of flux N= number of turns in coil

Question 31

Electrons flow oppositely to

Answer 31

Conventional current

Question 32

If there is no change in flux then no

Answer 32

Emf will be created, so no current will be created

Question 33

What is a solenoid

Answer 33

Lots of coils round an iron core

Question 34

Two types of transformers

Answer 34

Step up And Step down

Question 35

Equation for transformers

Answer 35

Vp/Np = Vs/Ns

Question 36

As there is no energy lost, the rate of change of flux in primary coil is

Answer 36

The rate of change of flux in the secondary coil

Question 37

Due to conservation of energy, in transformers what is the eq for power

Answer 37

Power before = power after IpVp = IsVs (not really the case in reality)

Question 38

For step up transformers compare velocities

Answer 38

Vout > Vin Therefore I out < I in

Question 39

For step down transformers compare voltage

Answer 39

Vin > Vout Therefore I in < I out

Question 40

Eq for sinusoidal alternating voltage

Answer 40

V= V0 sin 2(pie) ft

Question 41

Eq for sinusoidal alternating current

Answer 41

I= I0 sin 2(pie) ft

Question 42

Root mean square voltage eq | Alternating

Answer 42

The peak voltage / the square root of 2

Question 43

Root mean square current eq | Alternating

Answer 43

The peak current / square root of 2

Question 44

Eq for sinusoidal alternating voltage | Alternating

Answer 44

V= V0 sin 2(pie) ft

Question 45

Eq for sinusoidal alternating current | Alternating

Answer 45

I= I0 sin 2(pie) ft

Question 46

What is magnetic flux density

Answer 46

The strength of a magnetic field at a point in space Represented by the density of field lines at that point

Question 47

What is magnetic flux

Answer 47

The amount of field passing through perpendicularly a defined area Represented in diagrams by the number of lines passing through an area

Question 48

Flux through coil equation

Answer 48

BA Flux density x area

Question 49

Flux linkage equation

Answer 49

N BA Number of coils x flux density x area