IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => IGCSE/ GCSE => Sciences => Topic started by: esso on June 09, 2009, 05:44:26 am
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need help in the questions in the attachment .....
these r from an old paper....
try it out nd tell me de answers....
Thanks in advance.... ;)
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i think the answer should be D...
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34 D (transformer..magnetic field to be created )
38 D( 16-8-4, two half lives..so 12000)
31 A(a 1A fuse will be the first to melt and break the circuit..the values of the circuit breaker and the other fuse is higher and switch can be possible only if it is switched off)
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34 D (transformer..magnetic field to be created )
38 D( 16-8-4, two half lives..so 12000)
31 A(a 1A fuse will be the first to melt and break the circuit..the values of the circuit breaker and the other fuse is higher and switch can be possible only if it is switched off)
Thanks for d help ... bt wat abt 35
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i think the answer should be D...
Thanks for the help u 2 +rep
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34 D (transformer..magnetic field to be created )
38 D( 16-8-4, two half lives..so 12000)
31 A(a 1A fuse will be the first to melt and break the circuit..the values of the circuit breaker and the other fuse is higher and switch can be possible only if it is switched off)
Thanks for d help ... bt wat abt 35
sorry i didn't see 35...it is A because more current flows through the circuit
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but why is 35 A ???
since the resistance decreases .....
the voltage decreases....
as a result less voltage reaches the motor and rotates slower.....
i think its C....
do any one have the ms????????
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can i know why or how did u know 38 was D ?
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but why is 35 A ???
since the resistance decreases .....
the voltage decreases....
as a result less voltage reaches the motor and rotates slower.....
i think its C....
do any one have the ms????????
It's D because when the current increases the coil in the motor rotates faster(it's a motor when u increase the current the field lines are cut faster)
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can i know why or how did u know 38 was D ?
when the organism died the count rate was 16
when they found the fossil it gave four counts only. The half life is 6000...from 16 to 8 is 1 and from 8 to4 is the second. So 2 half lives are 12000 years. The fossil is 12000 years old
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ok
38 is D
because since it emits 16 particles per min, from 16 - 8 - 4 is 2 half lives
now since 1 half live is 6000, 2 half lives prove its 12000 years old :D
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Please post this in the physics help section
and tell my, for the motor question, which year is it from? ill see if i have the markscheme!
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its from may 1995...can any one find the markscheme?????
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here
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Thanks astar....
but why is 35 D ???????
need an answer please...
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its D
because when u pass current through the iron core a magnetic field is induced at one end.a magnetic field is also induced at the other end..causing a voltage and thus higher or lower currnet *depends on the tansformer whether its a step down or step up transformer*
hope it helped ;D :D
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Thanks astar....
but why is 35 D ???????
need an answer please...
The motor stops because the voltage across it is zero.
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yah understood .... Thanks everyone for the help ;)
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but astar how is the pd decreasing, cuz the current is increasing( resistance is reduced.) And when the current increases rotation in a motor is faster no?? Plz explain astar...i too am giving my exam tomorrow
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Voltage Decreases because voltage is the pressure basically, so if there is less resistance then this means that ekectrons will produce a less effort to pass through decreasing the pressure, and since Voltage is INVERSLY proportional to current, then when voltage decreases this casuses the current to increase causing the motor to spin faster
Right Sir??
Thanks
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Voltage Decreases because voltage is the pressure basically, so if there is less resistance then this means that ekectrons will produce a less effort to pass through decreasing the pressure, and since Voltage is INVERSLY proportional to current, then when voltage decreases this casuses the current to increase causing the motor to spin faster
Right Sir??
Thanks
that is what i thought but the mark scheme says the motor stops... ???
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but astar how is the pd decreasing, cuz the current is increasing( resistance is reduced.) And when the current increases rotation in a motor is faster no?? Plz explain astar...i too am giving my exam tomorrow
The voltage a cross the motor is the voltage across that part of the resistor between X and th other wire connecting the motor to the circuit. If you move the conact at x to the bottom of the resistor this voltage will be zero and the current and voltage and resistance in the circuit is irrelevant. Hence the motor stops
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but astar how is the pd decreasing, cuz the current is increasing( resistance is reduced.) And when the current increases rotation in a motor is faster no?? Plz explain astar...i too am giving my exam tomorrow
The voltage a cross the motor is the voltage across that part of the resistor between X and th other wire connecting the motor to the circuit. If you move the conact at x to the bottom of the resistor this voltage will be zero and the current and voltage and resistance in the circuit is irrelevant. Hence the motor stops
ohh so ok V and I are inversely proporional but when V=0 (zero), then no current can occur right??
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their is this question in may 2007 no 3 cud sum 1 explain the answer to me?
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but astar how is the pd decreasing, cuz the current is increasing( resistance is reduced.) And when the current increases rotation in a motor is faster no?? Plz explain astar...i too am giving my exam tomorrow
The voltage a cross the motor is the voltage across that part of the resistor between X and th other wire connecting the motor to the circuit. If you move the conact at x to the bottom of the resistor this voltage will be zero and the current and voltage and resistance in the circuit is irrelevant. Hence the motor stops
ok so when V is 0, rest pf the things are not to be considered..so now i understand that the resistor is acting like a potential divider.
thanks sir
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but astar how is the pd decreasing, cuz the current is increasing( resistance is reduced.) And when the current increases rotation in a motor is faster no?? Plz explain astar...i too am giving my exam tomorrow
The voltage a cross the motor is the voltage across that part of the resistor between X and th other wire connecting the motor to the circuit. If you move the conact at x to the bottom of the resistor this voltage will be zero and the current and voltage and resistance in the circuit is irrelevant. Hence the motor stops
yeah thanks sir, i understand too :)
ok so when V is 0, rest pf the things are not to be considered..so now i understand that the resistor is acting like a potential divider.
thanks sir
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but astar how is the pd decreasing, cuz the current is increasing( resistance is reduced.) And when the current increases rotation in a motor is faster no?? Plz explain astar...i too am giving my exam tomorrow
The voltage a cross the motor is the voltage across that part of the resistor between X and th other wire connecting the motor to the circuit. If you move the conact at x to the bottom of the resistor this voltage will be zero and the current and voltage and resistance in the circuit is irrelevant. Hence the motor stops
ohh so ok V and I are inversely proporional but when V=0 (zero), then no current can occur right??
No Vmotor=(Vsupply*Rout/(Rout+R) where R is the other resistance in the cicuit
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Yes it is a potential divider
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hey Astar cud u help with nov 2006 p1 q3?plz it will be really appreciated
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hey Astar cud u help with nov 2006 p1 q3?plz it will be really appreciated
60km/h
30km in 1/2 hour..so in 1 hour it will be 60
ans is D
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hey Astar cud u help with nov 2006 p1 q3?plz it will be really appreciated
60km/h
30km in 1/2 hour..so in 1 hour it will be 60
ans is D
HEY THANKS NID U REALLY HELPED I HAD NO IDEA HOW TO THESE QUESTIONS!BUT NOW I DO!
TAKE MY ADVICE AND BECOME A TEACHER!LOL U WILL ROCK 8)
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hey Astar cud u help with nov 2006 p1 q3?plz it will be really appreciated
60km/h
30km in 1/2 hour..so in 1 hour it will be 60
ans is D
HEY THANKS NID U REALLY HELPED I HAD NO IDEA HOW TO THESE QUESTIONS!BUT NOW I DO!
TAKE MY ADVICE AND BECOME A TEACHER!LOL U WILL ROCK 8)
I don't mind teaching chem and bio..not very good at explaining physics,escpecially when it doesn't have calculations. Physics calculations are easier to explain than the theory part of it.
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Thanks
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Thanks
???
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I cant answer questions now cos am on a mobile phone
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Anyone has marking scheme of November 1995 paper 1
or can you answer question 31
Really appreciate it.
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Anyone has marking scheme of November 1995 paper 1
or can you answer question 31
Really appreciate it.
yes i do........
the ans is B