unit 4 - magnetism

Question 1

Magnetic Field lines defination

Answer 1

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

Question 2

Properties of Magnetic Field Line

Answer 2

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

Question 3

Why cant 2 MFLs intersect

Answer 3

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

Question 4

Conventions of Magnetic Field - Going into the page

Answer 4

North pole and represented with Circles (remember using GON)

Question 5

Conventions of Magnetic Field - Coming out of the page

Answer 5

South pole and represented with X

Question 6

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

Answer 6

Using Right hand grip 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.

Question 7

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

Answer 7

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

Question 8

Factors affecting MF strength generated by a Solenoid

Answer 8

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

Question 9

formula for force acting on a straight current carrying wire

Answer 9

F = BIL

B = strength of external magentic field in tesla

Question 10

Direction for magnetic force for straight current carrying wire

Answer 10

Using right hand palm rule

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

Question 11

formula for force acting on a moving charge

Answer 11

F = B * q * v

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

Question 12

Direction of magnetic force on a moving charge

Answer 12

Using right hand palm rule

Question 13

1 amp current

Answer 13

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

Question 14

Magnetic Flux defination

Answer 14

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

Question 15

Formula for magnetic flux

Answer 15

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

Question 16

Magnetic Flux linkage

Answer 16

Magnetic flux lineage associated with ‘N’ number of coils

Question 17

Formula for magnetic flux linkage

Answer 17

ɸ = NBAcosθ

Question 18

Faraday’s law of electromagnetic induction definition

Answer 18

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

Question 19

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

Answer 19

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.

Question 20

Factors affecting the induced Electromotive Force?

Answer 20

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

Question 21

Faraday’s 3 experiments what were the reasons?

Answer 21

1) Bar magnet in relative motion with a Solenoid (to see if induced current can be produced w/ bar magnet)
2) To see if a bar magnet is required or will an electromagnet work?
3) to see if relative motion is required to generate electricity (ans - no)

Question 22

Electromagnet

Answer 22

Device which exhibits a MF when current flows through it

Question 23

How to create EMF/voltage using magnetic flux linkage in real life?

Answer 23

By changing the angle formed the direction of magnetic field and the perpendicular to the area of cross section

This is changed in real life by using Alternating current instead of direct current

Question 24

Alternating Current

Answer 24

Flow of current changes periodically, the +ve and -ve terminals change

Question 25

Which is more common AC or DC? and why

Answer 25

AC as it is easier to transport from one place to another

Question 26

Direct Current

Answer 26

No change in flow of current

Question 27

Transformer

Answer 27

A device which creates and releases AC and is a device used to transmit electricity from the power generating station to the end user

Question 28

What happens in the primary of a Transformer

Answer 28

AC is inputted and that changes the flux linkage and this is transferred onto the secondary by the Laminated core

Question 29

What happens in the laminated core of a transform

Answer 29

Multiple plates are put together to restrict the flow of electrons

Question 30

Ideal transformer

Answer 30

No energy and flux lost as flux in primary and secondary remains the same

Question 31

Formula for ideal transformer

Answer 31

Vp/Vs = Is/Ip = Np/Ns

Question 32

Step Up transformer

Answer 32

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 greater than the number of coils at the secondary.
The current in primary is greater than the current at secondary

Question 33

Step down transformer

Answer 33

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