Physics Study thread - M&G (1 Viewer)

[MuffinMan]

The point of this thread is to start with the first dot point and post your answer to the dotpoint...i would start but i got a maths test tomorrow...so can someone else start?
thanks

 

[rama_v]

Explain why, using physics principles, many motors have resistors which need to be switched on when the motors are warming up.

 

[Xayma]

Explain why, using physics principles, many motors have resistors which need to be switched on when the motors are warming up.

No Back EMF, larger current present, burns out the wiring.

 

[rnitya_25]

slow progress ppl....anyone still doing this?

 

[3G'sMt5:16]

Man... this is lame... bwhhahah

I'll join if TONS of people would cccome and support this forum!

But anyways... who would study on the computer with their own notes... i'd rather put my notes on hardcopy myself and help myself.... it would take double time to cover the dot points if you guys do this


my gum -_-

 

[Sirius Black]

can i ask a related question here on back emf ?
As we know, in motors, there is start-up burn out risk bcoz no rotation-->no back emf-->large current=large emf/small resistence right?
If it is so, then back emf should be considered as useful thing but why later on we have to laminate iron core in order to prevent wastage of heat energy due to the eddy current as a result of back emf?

 

[Abtari]

first dotpoint ppl, hello? not straight into back emf!

 

[Abtari]

first dotpoint 1.1.1

discuss the effect on the magnitude of the force on a current-carrying conductor of variations in:
- the strength of the magnetic field in which it is located
- the magnitude of the current in the conductor
- the length of the conductor in the external magnetic field
- the angle between the direction of the external magnetic field and the direction of the length of the conductor


the force on a current-carrying conductor is directly proportional to:
1) the strength of the magnetic field (B), i.e. greater--> greater
2) the magnitude of the current in the conductor (I), i.e. greater--> greater
3) the length of the conductor in the magnetic field (l), i.e. greater-->greater
4) the angle between the direction of the external magnetic field and the direction of the length of the conductor, provided the angle is acute. (hence maximum force when this angle is 90 degrees).

 

[sunjet]

force = bIlsintheta

 

[MuffinMan]

o dear...i totally forgot about this thread

 

[Abtari]

lol...haha take your time... its everyone's job remember? (although i must say, u do a heck of a job HSC_sUcKsSsS)

 

[Emma-Jayde]

Eh, seems like this may be useful.....

Sooo...



Define torque as the turning moment of a force using: t = Fd


Torque is defined as the turning moment of a force, that is, t = Fd , where:
t is the torque
F is the component of the applied force perpendicular to the axis of rotation
d is the perpendicular distance from the axis to the line of action of the force.

The force is applied acting in a clockwise or anticlockwise direction about an axis of rotation.

 

[sunjet]

1. Explain how a DC and AC motor works.
2. Explain the differences between them and evaluate.
3. Explain how an AC induction motor works.

Theres some questions

 

[3G'sMt5:16]

i'm bored... so i'm doing this... lOLz!

SPACE DOT POINT ---> identify that if c is constant then space and time become relative

HSC ONLINE says : In CLASSICAL physics, space (that is, position, displacement and velocity, including the speed of light) can be relative to an observer, but time is an absolute quantity, passing identically for everybody.

thats a quote froom HSC online... hmmmm

I just wanted to tell ya that classical physics DISCARDS einstein and his two postulates involving relativity. Albert the great thinker said in his second postulate said that:

1. The speed of light C (3.0 x 10^8 m.s^-1 i think) is ALWAYS constant regardless of your/ the observers inertial frame of reference.

And that his first postulate posed that

2. In all inertial frames of reference the laws of physics (both modern and quantum physics.. except for classical) are ALWAYS the same (e.g. couloumbs laws on charges (q) =) ).

In other words.. when you see classical phys. it means it opposes relativity... this also covers some of the aspects in the other dot point here --> outline the nature of inertial frames of reference, discuss the principle of relativity, (esp) analyse and interpret some of Einstein’s thought experiments involving mirrors and trains and discuss the relationship between thought and reality and many more... you'll find that relativity dot points all interrelate to a certain degree.

not sure about the classical physics in the topic for black body radiation though... anybody know what i'm talking about?? (something about the graph of temperature VS absorption)... hmmmmm

 

[3G'sMt5:16]

force = bIlsintheta

*YAWWNS* dude... where n the number of turns.. lalala

 

[velox]

it should be nBILsin theta

 

[3G'sMt5:16]

ber ber berrrr derrrrr fleddssssss

lol

 

[lilkatie]

Ok lets get this rolling again people...
assess affect of Ac generators on society and environment
-brought electricity = source energy
-source power can be a long away from where the power is to be used
-allowed developmemt of many technologies
-power generation = greenhouse gases and CO2
- in workplace = allowed electromagnets to be utilised = machinery faster and more efficient

=p

 

[DigitalFortress]

it should be nBILsin theta

I don't get this.
I always thought it was nBIAcos Theta , BIL sin theta , qvB sin theta,

How does a length have number of turns ?

 

[tennille]

I don't get this.
I always thought it was nBIAcos Theta , BIL sin theta , qvB sin theta,

How does a length have number of turns ?

Hmmm...I thought that as well. I looked at the hsc.csu.edu.au site, and it doesn't state anything about nBIlsintheta, only nBIAcostheta and BIlsintheta.