Physics doubts

[thecandydoll]

Oct/Nov 2005 Q6 (c) (ii)
May/June 2004 Q5 (d) (i and ii)
O/N 2003 Q4 (C)
What is resonant frequency?
M/J 2002 q6 (A)

[thecandydoll]

PS This is CIE

[Sue T]

i assume this is paper 4
your first ques: from the graph of change of flux u must draw induced e.m.f so the thing is
rate of change of flux ---> induced emf
rate of change of flux ---> gradient of the graph
so what you're plotting is basically the variation of the gradient with time
so from t=0 till t=T gradient is zero --> so draw a flat line on the x-axis
    from t=T till t=2T gradient suddenly rises and is constant and positive --> so a horizontal line in th +ve region of the y-axis is drawn
    from t=2T till t=3T gradient suddenly drops and is constant and negative and of a larger value than wat we've just seen --> so u draw a horizontal line on the negative y-axis region and make sure its lower than the first
ill try attaching it

[thecandydoll]

omg thanks a ton!Someone help me with the rest pleasee

[Sue T]

mj04 5di and ii) its a kind of a trick - peak and rms will be the same cuz this is a square wave and not a.c. - so u dont use the rms=peak/root2 rule
this is because as you now the reason for this rule for an ac wave is that the peak vaule in an ac wave only occurs for a moment and taking an average value of th current or voltage we would end up with a zero cuz the values are both positive and negative - --- but but look at this square wave - th peak value of 3 works cuz it occurs all th time

octnov03 - ammm if u put another capacitor in parallel  C_total=C_old + C_new
so there'll be less ripple (tried 2 sketch smthin approximate 4 u )

resonant frequency - u could google for a definition but if u want 2 understand it then i would say :every system (ex. bus car trolley phone watever) has a specific frequency of oscillation where th amplitude becomes max - anything beyond or less than that particular frequency wouldnt result in the same amplitude building up.

mj 2002 - you have the same situation as earlier but they gave you current u c - so think bout th fact that this current is proportional to th magnetic flux ryt? cuz th more current the more the magnetic field and the cutting of magnetic flux by the iron core - now that you've established that:
"the variation with current with respect to time is the same as the variation with flux with respect to time"
you in turn sketch the variation of th gradient with respect to time for your emf (rate of change of flux = induced emf)
so again  - ive attached it