Biology; Chemistry; Physics: Post your doubts here!

[convent2012]

cAn someBody plEase reVise aLl the experiMents in phYsics , thaNks in aDvance

 

[snowbrood]

can u please give the answers of this question paper? and can u please tell that is this only a practice paper or are these questions from recent past papers?

i am solving this on my own
Q1(i) diode
(ii) to prevent any current flowing into transistor. as such a large current could damage transistor
b(i) 6*2000/(5000+2000) =1.7 volts
b(ii) as the light intensity increases on LDR its resistance decreases this would increase the voltage across the resistor 2. Not gate would recognize this as "1" and convert it into "0" i.e current will not flow at the resistor. and as the transistor detects no current at its base so it would not switch on the collector emitter current. so the relay wont be switched on and thus bulbs wont light.
Q2a(i) transistor
Q2a(ii) increases and does not affect
Q2a(iii) this circuit could be used in green house.
Q3a when the sensor gets wet its resistance decreases the current flows in base of transistor. transistor switches on the collector emitter current and so bulbs would light.
b(i) in order to make no electrical connection between the two ciruits. the link is mechanical and magnetic. preventing any harm to the ciruit operating at low voltage.
b(ii) decreasing its voltage would switch on the circuit while increasing its voltage would switch off the ciruit.
Q4 a(i) this limits the amount of current flowing into the transistor to avoid damaging it.
ii(A) Water provides a conducting path for the probes.voltage at the base reaches 0.7 volts and the this switches on the transistor
ii(B) Transistor allows a large current to flow from collector to emitter. current flowing through relay creates the magnetic field which attracts the lever and allows current to flow in the buzzer which then sounds.
iii it can be used for warning of rain

 

[kitecrystal]

how to find age by using half-life,like in Q11 (b)(ii) of this 5054,w03Q11 c part?

 

[kitecrystal]

i am solving this on my own
Q1(i) diode
(ii) to prevent any current flowing into transistor. as such a large current could damage transistor
b(i) 6*2000/(5000+2000) =1.7 volts
b(ii) as the light intensity increases on LDR its resistance decreases this would increase the voltage across the resistor 2. Not gate would recognize this as "1" and convert it into "0" i.e current will not flow at the resistor. and as the transistor detects no current at its base so it would not switch on the collector emitter current. so the relay wont be switched on and thus bulbs wont light.
Q2a(i) transistor
Q2a(ii) increases and does not affect
Q2a(iii) this circuit could be used in green house.
Q3a when the sensor gets wet its resistance decreases the current flows in base of transistor. transistor switches on the collector emitter current and so bulbs would light.
b(i) in order to make no electrical connection between the two ciruits. the link is mechanical and magnetic. preventing any harm to the ciruit operating at low voltage.
b(ii) decreasing its voltage would switch on the circuit while increasing its voltage would switch off the ciruit.
Q4 a(i) this limits the amount of current flowing into the transistor to avoid damaging it.
ii(A) Water provides a conducting path for the probes.voltage at the base reaches 0.7 volts and the this switches on the transistor
ii(B) Transistor allows a large current to flow from collector to emitter. current flowing through relay creates the magnetic field which attracts the lever and allows current to flow in the buzzer which then sounds.
iii it can be used for warning of rain

which book is best to prepare for transistors??

 

[SalmanPakRocks]

how to find age by using half-life,like in Q11 (b)(ii) of this 5054,w03Q11 c part?

Simply half the value of the number of atoms/count rate present!

 

[kitecrystal]

Simply half the value of the number of atoms/count rate present!

thanks and will you please explain the specified question?

 

[snowbrood]

which book is best to prepare for transistors??

complete physics by stephen pople oxford publishing company

 

[snowbrood]

thanks and will you please explain the specified question?

u dont have to get worried abt transistor much all u got know is that once the voltage at its base is 0.7 volts it would work and the large current would flow from collector to emitter

 

[Ahmedfj]

biology 5090 2005 paper 1 mcq number 12 18 35 36
help asap !

 

[kitecrystal]

biology 5090 2005 paper 1 mcq number 12 18 35 36
help asap !

which paper, june or november?

 

[Ahmedfj]

which paper, june or november?

june

 

[Ahmedfj]

biology 5090 june 2005 paper 1 mcq number 12 18 35 36
biology 5090 june 2006 paper 1 mcq number 2 4 14 18 23 26 27 28

HELP ASAP and i want to know all about the type of graph shown in mcq 14 of june 5090 2006 paper 1

ASAP pls !!

 

[multixamza01]

biology 5090 june 2005 paper 1 mcq number 12 18 35 36
biology 5090 june 2006 paper 1 mcq number 2 4 14 18 23 26 27 28

HELP ASAP and i want to know all about the type of graph shown in mcq 14 of june 5090 2006 paper 1

ASAP pls !!

ASAP means '' as soon as possible ''
Not possible right now . Maybe later

 

[Ahmedfj]

ASAP means '' as soon as possible ''
Not possible right now . Maybe later

Dude i m really worried right now ... u know anyone on this forum who takes Biology in O'levels ????

 

[multixamza01]

Dude i m really worried right now ... u know anyone on this forum who takes Biology in O'levels ????

: raises hand in Hermione style :

 

[Ahmedfj]

: raises hand in Hermione style :

So hermione will u please help me to solve these mcqs ... i will give u an E-book if u help me

 

[Ahmedfj]

biology 5090 june 2005 paper 1 mcq number 12 18 35 36
biology 5090 june 2006 paper 1 mcq number 2 4 14 18 23 26 27 28

HELP ASAP and i want to know all about the type of graph shown in mcq 14 of june 5090 2006 paper 1

ASAP pls !!

anyone pleeeaaseee ????

 

[kitecrystal]

anyone pleeeaaseee ????

june05,..12.D because the roots may be cut or damaged while digging,so their surface area is reduced.Thus,wilting occurs.However,the stem can still function properly.
18.CMuscles that tolerate more lactate will allow more anaerobic respiration and so supply more energy, which
will allow the athlete to run faster or further, or both.
35.3 days of ovulation and two possible previous days as the sperms can live for 2 days.
36.its a fact.

 

[kitecrystal]

anyone pleeeaaseee ????

november 2006 Q2.C.The root hair cell will
take in soil water and become turgid. Hence the hair will aid support and is itself supported by the sap it contains. The question posed another problem in as much as cell Y (a xylem vessel) is lignified contains nocytoplasm or cell membrane when mature as drawn, and is incapable of taking in water by osmosis. It does,of course, provide support, but not due to turgor.
Q4.C.According to lock and key hypothesis,enzyme is lock and substrate is the key.Here,enzyme which acts on starch is amylase.
Q14.When the pressure in the ventricle rises above the pressure in the aorta, the semi-lunar valve is forced open.
It closes as the pressure falls below the aorta pressure.
Q18.A.As the peas respire and use oxygen, the volume of gas in the tube will
decrease because the carbon dioxide that is produced is absorbed immediately by the sodium hydroxide.
Q23.A.Its the shoulder joint(ball and socket).The muscles contract and relax as is evident by their shapes.
Q26.B.Fungi have thread-like bodies known as mycelium.
Q27.D.“Batch” production (which is not
usually as economic as “continuous”) is characterised by starting each batch afresh and the product is
removed before cleaning the vessel and restarting the process.
Q28.C.Energy is lost at every level of a biological system.All other options are correct.

 

[Ahmedfj]

november 2006 Q2.C.The root hair cell will
take in soil water and become turgid. Hence the hair will aid support and is itself supported by the sap it contains. The question posed another problem in as much as cell Y (a xylem vessel) is lignified contains nocytoplasm or cell membrane when mature as drawn, and is incapable of taking in water by osmosis. It does,of course, provide support, but not due to turgor.
Q4.C.According to lock and key hypothesis,enzyme is lock and substrate is the key.Here,enzyme which acts on starch is amylase.
Q14.When the pressure in the ventricle rises above the pressure in the aorta, the semi-lunar valve is forced open.
It closes as the pressure falls below the aorta pressure.
Q18.A.As the peas respire and use oxygen, the volume of gas in the tube will
decrease because the carbon dioxide that is produced is absorbed immediately by the sodium hydroxide.
Q23.A.Its the shoulder joint(ball and socket).The muscles contract and relax as is evident by their shapes.
Q26.B.Fungi have thread-like bodies known as mycelium.
Q27.D.“Batch” production (which is not
usually as economic as “continuous”) is characterised by starting each batch afresh and the product is
removed before cleaning the vessel and restarting the process.
Q28.C.Energy is lost at every level of a biological system.All other options are correct.

thanks so much .. btw i dont know how to read ventricle graphs (mcq 14 june 2006) and i have seen that there are 4-5 questions concerning these types of graphs in past papers so can u please explain how to read these graphs