Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

G9 + 10 physics > unit 4 - magnetism > Flashcards

unit 4 - magnetism Flashcards

1
Q

Magnetic Field lines defination

A

Imaginary path in which the magnetic north monopole travels in the presence of an External Magnetic Field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Magnetic field defination

A

Area around a magnet in which the effects of magnetism can be felt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Properties of Magnetic Field Line

A

1) The direction of MFLs indicate the direction of the MF field at that point
2) The density of MFLs in an indicator of the magnetic field strength in that area
3) MFLs form close loops
4) MFLs appear to emerge from the North Pole and Appear to terminate at the south pole
5) No 2 field lines every intersect each other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why cant 2 MFLs intersect

A

Because the magnetic north monopole will then have 2 directions to travel which isnt possible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Conventions of Magnetic Field - coming out of the page

A

represented with Circles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Conventions of Magnetic Field - going into the page

A

represented with X

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How to determine direction of magnetic field in straight current carrying wire

A

Using Right hand grip rule or Maxwells right hand thumb rule, Imagine holding the wire in ur right hand such that the thumb represents the direction of conventional current, then the 4 fingers represent the direction of magnetic field.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How to determine the direction of magnetic field in solenoid/loop

A

Using right hand grip rule modified

Out stretch the 4 fingers of your hand to represent the direction of conventional current and then the direction of the magnetic field is represented with ur thumb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Factors affecting MF strength generated by a Solenoid

A

1) No. of coils
2) Current and PD
3) No. of coils per unit length
4) Material of the core
5) Distance of point of measurement of MF from solenoid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how to find Magnitude and Direction of force acting on a straight current carrying wire

A

Magnitude = F = BIL
B = strength of external magentic field in tesla

Direction = Right hand Palm rule/ Flemming’s Left hand ruke

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

right hand palm rule

A

Outstretch the 4 fingers of you right hand to rep the direction of MF and the thumb to rep the direction of conventional current. Then the direction of palm indicates the direction of Magnetic Force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Magnitude and Direction for force acting on a moving charge

A

Magnitude: F = B * q * v

v = speed of moving body
q = charge on moving body
B = strength of external magnetic field

Direction: Right hand palm rule or Flemings left hand rule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

1 amp current

A

If the force per unit length between 2 parallel current carrying wires carrying the same amount of current separated by 1 mtr distance in air or vacuum is 2 * 10^-7 Nm-1, then the current flowing through each wire is said to be 1mp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Magnetic Flux defination

A

Measure of the no. of field lines passing parallel to perpendicular to the area of cross section

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Formula for magnetic flux

A

ɸ = BAcosθ

B = Mf strength
A = area of cross section of loop
θ = Angle formed between direction of MF and perpendicular to the area of cross section

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Magnetic Flux linkage

A

Magnetic flux lineage associated with ‘N’ number of coils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Formula for magnetic flux linkage

A

ɸ = NBAcosθ

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Faraday’s law of electromagnetic induction definition

A

The induced potential difference/EMF is directly proportional to the negative rate of change in magnetic flux linkage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what should be done to constantly produce voltage through Magnetic flux linkeage

A

Magnetic Flux linkage must be constantly changing over a short period of time to sustainably produce voltage. The shorter the time, the greater the voltage produced.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Factors affecting the induced Electromotive Force?

A

1) No. of coils
2) Strength of external magnetic field
3) Area of cross section of loop
4) Angle formed between the direction of MF and the perpendicular to the area of cross section

21
Q

Faraday’s 1st experiments what were the reasons and conclusions?

A

1) Bar magnet in relative motion with a Solenoid

Rationale - to see if induced current can be produced w/ bar magnet and solenoid

Conclusion was that relative motion changes the MF ( by changing how cloe the solenoid is to the magnet) and creates induced EMF

22
Q

Faraday’s second experiemnt, rationale and observation

A

To find out if a bar magnet was necessary

Rationale - Is a bar magnet required or will an electro magnet also work

Observation - An electro magnetic also works as constantly turning the electromagnet on and off changes the value of its MF strength, and hence creates a change in the flux linkage, causing an Induced EMF

23
Q

Faraday’s 3rd experiemnt, rationale and observation

A

Is Relative motion required between bar magnet and coil?

Rationale - To find other factors which can change flux linkage and produce voltage

Observation - Relative motion isnt required, by changing the any factor affecting flux linkage such as MF strenght, angle theta and area of cross section of wire, voltage can be made

24
Q

Basic discovery by faraday in terms of magentic fields and current

A

A steady magnetic field doesnt produce a current, but a changing MF does produced a current

25
How can we sustain the infuced EMF created by Flux linkage
Magentic flux linkage must change over a very short period of time and must contstantly keep changing. If the change happens in a shorter period of time, then the voltage produced will be higher
26
Electromagnet
Device which exhibits a MF when current flows through it
27
How to create EMF/voltage using magnetic flux linkage in real life in power plants?
By changing the angle formed the direction of magnetic field and the perpendicular to the area of cross section
28
Alternating Current
Flow of current changes periodically, the +ve and -ve terminals change
29
Which is more common AC or DC? and why
AC as it is easier to transport from one place to another. It can be easily stepped up and down in voltage using transformers, which allows for efficient transmission over long distances by minimizing power loss. Many factories already produce AC and hence there isnt a need for an extra conversion step
30
Direct Current
No change in flow of current
31
Transformer
A device which minimises the power lost and is a device used to transmit electricity from the power generating station to the end user
32
What happens in the primary of a Transformer
AC is inputted and that changes the flux linkage and this is transferred onto the secondary by the Laminated core
33
What happens in the laminated core of a transform
Multiple plates are put together to restrict the flow of electrons and minimise power loss. Generally made of a soft iron core and transfers the chnage in flux from the primary to the secondary
34
Ideal transformer
No energy and flux lost as flux in primary and secondary remains the same
35
Formula for ideal transformer
Vp/Vs = Is/Ip = Np/Ns
36
Step Up transformer
Used at the Power generating station It is where the voltage at secondary is greater than voltage at primary. To achieve this, the number of coils at the primary is less than the number of coils at the secondary. The current in primary is greater than the current at secondary This si done to minimise power loss. As electrical energy is transported at high voltage to minise power, to acheiev this high voltage, we must use Step up transformers
37
Step down transformer
Used at the End user It is where the voltage at the primary is greater than the voltage at the secondary by making the number of coils in the primary more than the number of coils at the secondary The current as secondary is greater than the current in primary
38
Appartus used to measure Magentic field strength
Vernier Magnetic Field sensor to capture the data and LabQuest to display the readings
39
When is Magnetic flux linkeage maximum and 0
It is 0 when the perpendicular to the area of cross section is perpendicular to the field line, ie when cos = 0 It is max when perpendicular to the area of cross section is parallel to the magnetic feild lines, ie when cos = 1
40
Electromotive Force
Voltage/Potential Differene
41
How do turbines generate EMF
The coil in the turbine rotates in the prescnce of an external Magnetific Feidl. This rotation causes a change in the value of theta which chanegs the value of flux linkage. The turbine rotates very fast and hence flux linkage is changed very often, producing sustainable AC current
42
Method to rememebr flemmings left hand rule
FBI Put fingers in proper left hand rule position, go from thumb to middle denoting F,B and I to one finger Thumb = F = force fo MF Index = B = MF direction Middle = I = covnentional current
43
Flemmings left hand rue
Outstretch the thumb index and middle finger of your left hand, all perpendicualr to each other. If the index finger repsents the direction of magentic field, and the middle finger repsents the direction of conventional current, then the direction of thumb repsents the directon of magnetic force
44
How does an AC generator induce an electromotive force (emf)?
The coil/armature attached to the turbine rotates, changing the value of theta in flux linkage and hence according to faraday's law, the change happens over a very short period of time, creting an induced EMF
45
How does the flow of current change in an AC genetaor
Once the armature si perpendicular to the magnetic field the current flow changes. This is because the side of the coil which was originally upwards, had current flowing in and vice versa for the other side. But now since the origina side that was up is going downwards, the current must flow out of it.
46
Use of slip rings and brushes in AC geneator
To avoid the twisting and turning of wires we connect the armautre to slip rings, which one side of the armature connected to one slip ring. Each slip ring also has a brush attahced to it, which allows for constant contact beween the ring and the external circuit
47
Use of commutators in DC motor
The commutator we use is a split ring, which is signular ring with two splits in it which help connect the brushes to their respectvies wires to allow current to flow in one direction (direct current). Each side of the split ring is connected to one end of the armature
48
What happens wehn the armature is perpendicualr to the MF in DC motor
When the armature is perpendicular to the MF, to avoid the current changing directions, the brushes come in contact with the opposite side of the split ring as they were before allowing for current to flow in the same direction. Both brishes touch the other side of the ring and allow current to flow in one direction
49
the greater the change in the magnetic flux linkage (differnce in values) equal to....
A greater Induced EMF and hence a greater current

G9 + 10 physics (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions