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Physics AS 2 > Chapter 6- Magnetic Fields > Flashcards

Chapter 6- Magnetic Fields Flashcards

1
Q

Magnetic field definition

A

A region in which magnetic materials experience a force

Field can be produced in three dimensions

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2
Q

Magnetic fields lines flow from

A

North to south

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3
Q

Neutral point is located

A

Somewhere between the north and south poles

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

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4
Q

What else produces magnetic fields

A

Electric currents

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5
Q

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

A

Circle with a dot inside it

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6
Q

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

A

A circle with a cross inside it

Like a screw

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7
Q

A spring like coil is called a

A

Solenoid

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8
Q

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

A

F= B IL

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9
Q

What is the strength of a magnetic field called

A

Called the magnetic flux density

(Symbol of B in BIL

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10
Q

For BIL to work the wire…

A

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

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11
Q

Unit of magnetic flux density

A

Tesla (T)

Or NA^-1 m^-1

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12
Q

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

A

Left hand rule

Force= thumb (forceful finger)
Field= first finger 
Current= third finger (curls to make a 'c')
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13
Q

When an electron moves in an electric field we get

A

Circular motion

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14
Q

BIL used for

A

Current carrying wires

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15
Q

BeV used for

A

Single charges

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16
Q

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

A

The direction of electron is in opposite direction to current flow

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17
Q

There is no work done at 90* so electron…

A

Never loses energy, so remains in the orbit

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18
Q

For a current in a wire it is

A

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)

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19
Q

What is the Hall effect

A

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

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20
Q

Voltage eq for electric field

21
Q

Magnetic flux density symbol

22
Q

Flux is the idea of

A

Total field lines captured within an area

23
Q

To get an increase in flux

A

Increase area

Increase magnetic flux density

24
Q

Flux symbol

25
Q

Flux unit

A

Measured in Weber Wb Tm^2

26
Q

Won’t capture anything if not in

A

Perpendicular circumstances

27
Q

Faraday’s law

A

Emf= the rate of change in flux

28
Q

A change in flux causes

A

A current to be induced

29
Q

Lenz’s law

A

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)

30
Q

Equation where Lenz’s law is seen

A

Emf= -N x rate of change of flux

N= number of turns in coil

31
Q

Electrons flow oppositely to

A

Conventional current

32
Q

If there is no change in flux then no

A

Emf will be created, so no current will be created

33
Q

What is a solenoid

A

Lots of coils round an iron core

34
Q

Two types of transformers

A

Step up
And
Step down

35
Q

Equation for transformers

A

Vp/Np = Vs/Ns

36
Q

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

A

The rate of change of flux in the secondary coil

37
Q

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

A

Power before = power after

IpVp = IsVs

(not really the case in reality)

38
Q

For step up transformers compare velocities

A

Vout > Vin

Therefore

I out < I in

39
Q

For step down transformers compare voltage

A

Vin > Vout

Therefore

I in < I out

40
Q

Eq for sinusoidal alternating voltage

A

V= V0 sin 2(pie) ft

41
Q

Eq for sinusoidal alternating current

A

I= I0 sin 2(pie) ft

42
Q

Root mean square voltage eq

Alternating

A

The peak voltage / the square root of 2

43
Q

Root mean square current eq

Alternating

A

The peak current / square root of 2

44
Q

Eq for sinusoidal alternating voltage

Alternating

A

V= V0 sin 2(pie) ft

45
Q

Eq for sinusoidal alternating current

Alternating

A

I= I0 sin 2(pie) ft

46
Q

What is magnetic flux density

A

The strength of a magnetic field at a point in space

Represented by the density of field lines at that point

47
Q

What is magnetic flux

A

The amount of field passing through perpendicularly a defined area

Represented in diagrams by the number of lines passing through an area

48
Q

Flux through coil equation

A

BA

Flux density x area

49
Q

Flux linkage equation

A

N BA

Number of coils x flux density x area

Physics AS 2 (14 decks)

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