Physics Help HERE ONLY !!

[MaNa]

hey guyz !!!
i need help wid nov 08 1st variant q 5 c

(c) Using a 40 W heater, 16.3 g of ice is melted in 2.0 minutes. The heater is then switched
off. In a further 2.0 minutes, 2.1 g of ice is melted.
Calculate the value of the specific latent heat of fusion of ice from these results.

mass -16.3-2.1=14.2
latens heat of fusion= energy
therefore 40*120=4800J
ther fore latent heat of fusion equals
4800/14.2
338J/g
hopes that explians

[Tutu_93]

I have a question in may june 2000 paper 3 10 c
What do the mean when they say that Gama rays interaction with gas molecules is very less

[annie_angel]

can anyone help wid the time base control ; base emitter collector and how the resistance works??

[Shogun]

2a) put different value of masses on bothe sides of the pivot  but make sure tht after using the formula (fxd) (where

f=force and d=distance) the product must be same. (then only they are balanced i.e in equilibrium)

 the distance are given for each hole to the pivot. so i recomend to take the first hole(with distance 4cm) and add mass 200g at one side of the pivot. and on the other side,  add mass 100g on the second hole (with disatnce 8 cm from teh pivot)

so when using the formula "fxd " u get on one side: 200x4=800N
                                                     and                                       
                                                   on the other side: 100x8=800N
                         - see both have the same product so it is now they are balanced(in equilibrium)


ans2b) the disc does not move or rotate as u put the mass so they are balanced so no turning effect which means no moment.

c)use formula "fxd"
               200x4=800N
               100x8=800N

d)this is the force of pivot which is downwar to get tht simply add the masses u put
100+800=900g

but rmember u can choose any mass at any distance but the product with equation "fxd" must be same

thts all,hope this helped, any confusion or difficulties or help u need, im all here

Hey,the formula for calculating the moment is f*d, and when we multiply 200g by 4cm, aren't we multiplying the mass by the distance? Aren't we first suppossed to convert the mass into force by multiplying it with 10 (F=ma)? and the unit for moment is supposed to be Nm, isn't it? Please help. Thanks in advance

true, sorry. so then we have to multiply them by 10, however we get same product, but u must multiply by 10
cuz mass x10 , but first we must convert the masses to killogram then multiply by 10 to get the force. but then thank u bani for correcting me

[Shogun]

can anyone help wid the time base control ; base emitter collector and how the resistance works??

the time base system works for the x plates on the cathode ray osclliscope(CRO), the thing is tht, dpending on time the voltage goes zero between the plates then after acertan period of time say 0.5 secs the voltage gose up to its original value, how does this help? the x plate is ment to let the beams of electrons move horizonataly (left and right) so it hits the screen (on both the left and right side). so to do this, lets say abeam of elctrones in an CRO is coming and as it passes through the x plates(which is charged with postive and negative charge) the beam of electron (which is negative in charge) deflects towards the postive charge plates.

lets say the positive plate is aranged on the right, so when thier is voltage the beam deflects to the right after CERTAIN SET TIME the voltage goes zero (so no charged plate) and the beam returns to its original path (i.e the left side) then again after a certain set time the voltage goes up and the beam of electrons deflects to the right again.. so this is how the beam moves right and left with the help of x plates whic is TIME BASE system.

base emiter stuff...
the base  and emmiter and collector wires are used in a transistor. the for the lamp to work (which is uually placed on the path of colletor emitter path) there must be a current on the base current and there must be a suitable potential difference of 0.6v across the base emitter path.

these conditions are needed for the transistor to work which acts as an automatic switch to switch on the lamp (which is usually placed in the collector -emitter path)

resistance stuff,
they say to the current "get the hell outta here" , u see they act as aopposition to the flow of current in the circuit, it does not let the current to pass through. it blocks the path of the current. with variable resistor u can change the amount of blockage, which means u can allow certain ammount of current to pass and flow through.

any more help or confusion or difficulties,plz do ask me.

[emi]

can some one explain for me for each of " alpha, gama, beta " radiations their

deflection in magnetic field
deflection in an electric field


thanks

[Shogun]

can some one explain for me for each of " alpha, gama, beta " radiations their

deflection in magnetic field
deflection in an electric field


thanks

deflections of rays in magnetic fields
alpha is positively charged so in magnetic field in to the paper (the north pole faced towards a paper) (uding flemings left hand u point ure index finger just like the way u would point at somone and with the thumb up and ure middle finger pointing towards the right(which is the direction alpha rays)) so doing this would indicate tht alpha rays deflects upwards.
however the beta rays(negatively charges) moves opposite to the deflection of alpha rays (i.e downwards but with the same conditions set as experssed for the alpha rays)
whereas in gamma rays, no deflection in magntic field.

deflections of rays in an electrical field.
lets say there are 2 charged plates place over another(with gap inbetwwen), one is postively charged plate which is for example the upper plate, and the lower plate is negatively charged. alpha rays deflect yowards the negative side (i.e downwards) as it is postively charged, whereas the beta rays deflects towards the positively charge plate(i.e upwards, just opposite of alpha rays). gamma rays do not deflect in electric fields either.

hope this helped, any confusion difficulties or help needed, plz do ask me

[emi]

thanks shogun that was great help .
and i understood each word you said  =]

<33

[Shogun]

ure welcome

[Tako93]

mmmm

i was wondering if there are a any revision notes which may help ??>

THX

[MaNa]

can sme body explain  MCQ
Paper 1 (2008may/june)
Q-37
n one more thing
Beta particals are elctions, n electrons are found in the OUTER ORBIT right
so in Q -38 (same year/session) the ans in A how?>

[astarmathsandphysics]

can sme body explain  MCQ
Paper 1 (2008may/june)
Q-37
n one more thing
Beta particals are elctions, n electrons are found in the OUTER ORBIT right
so in Q -38 (same year/session) the ans in A how?>

c.the voltage is in the ratio of the resistances

All radiation comes from the nuclues. A neutrom changes in to a proton: n>p⁺+e^-

[MaNa]

can sme body explain  MCQ
Paper 1 (2008may/june)
Q-37
n one more thing
Beta particals are elctions, n electrons are found in the OUTER ORBIT right
so in Q -38 (same year/session) the ans in A how?>

c.the voltage is in the ratio of the resistances

All radiation comes from the nuclues. A neutrom changes in to a proton: n>p⁺+e^-

but isnt it IR= V
so if R decreases V decreases too bcuz they r propotional:S

[jkiam11]

I have a question.

Why does cutting the magnetic fields with a wire generate a current?

[astarmathsandphysics]

It generates a force on the elctronds in the wire according to lenzs law V=-d/dt