Q&A - P5 Science

[Kangkangteo]

jojoberry:

Kangkangteo:

[quote=\"jojoberry\"]If the question asks to compare between both circuits - then bulbs in Circuit Y will be brighter than bulb in Circuit X because the effective resistance in Y is lower, so higher current will pass through each bulb. (but this is not the question in this case)

Sorry, the highlighted portion is incorrect. The brightness of the bulbs for X and Y will be the same since the voltage across each bulb is the same, the current through each bulb will also be the same, hence their brightness.

The overall resistance of the circuit is halved, but the overall current from the battery is doubled. So the battery will have a shorter life span.

Thanks for highlighting.
In this case - I overlooked the part where both circuits have different no of bulbs. So X and Y have the same brightness as the power generated by each bulb will be the same.

If we do have a case where the total no of bulbs in each circuit is the same, then bulbs in parallel circuit will be brighter.

Suppose emf of the circuit is 5V, resistance of each bulb is 10ohms.

In series circuit with 2 bulbs:
Effective resistance = 10 x 2=20
Current = V/R = 5/20 = 0.25 A

Power of each bulb: P=VI = 5 x 0.25 = 1.25W

In parallel circuit with 2 bulbs:
Effective resistance = 1/ (2/10) = 5
Current = v/R = 5/5 = 1.0A
Effective current in each bulb = 1.0 / 2 = 0.5A

Power of each bulb in parallel circuit : P = VI = 0.5 x 5 = 2.5W

Bulb in parallel circuit generates more power, and is brighter.[/quote]Sorry, if there were 2 bulbs in the series circuit, the voltage across each bulb would be halved, hence the current would also be halved. Thus the brightness of the 2 bulbs in the series circuit will be dimmer than the parallel circuit.

[Jamesbond]

http://i62.tinypic.com/2h85rnd.jpg\">

[Jamesbond]

http://i62.tinypic.com/2h85rnd.jpg\">

[HFPMAT]

this question can be answered by checking options only. it's not possible to answer just looking at graph as there can be two options for food producer C or B

Form options given, food producer can be A or B. In enclosure 1 , B is showing sharp decline in number while A increases. So B is producer while A is predator here.
But in enclosure two A is being eaten by another animal so A is predator in first while pray in second.
C shows decline in number in both enclosures so it is prey.
While D is increasing in number in enc. 2 so it is predator.
Ans:4

Jamesbond:

http://i62.tinypic.com/2h85rnd.jpg\">

[Jamesbond]

HFPMAT:

this question can be answered by checking options only. it's not possible to answer just looking at graph as there can be two options for food producer C or B

Form options given, food producer can be A or B. In enclosure 1 , B is showing sharp decline in number while A increases. So B is producer while A is predator here.
But in enclosure two A is being eaten by another animal so A is predator in first while pray in second.
C shows decline in number in both enclosures so it is prey.
While D is increasing in number in enc. 2 so it is predator.
Ans:4

Jamesbond:

http://i62.tinypic.com/2h85rnd.jpg\">

Thx for ur answer....by mistake I posted in P5 Science instead of P6 Science....shows I am stressed out :frustrated: :lightrod:

[HFPMAT]

Jamesbond:

HFPMAT:

this question can be answered by checking options only. it's not possible to answer just looking at graph as there can be two options for food producer C or B

Form options given, food producer can be A or B. In enclosure 1 , B is showing sharp decline in number while A increases. So B is producer while A is predator here.
But in enclosure two A is being eaten by another animal so A is predator in first while pray in second.
C shows decline in number in both enclosures so it is prey.
While D is increasing in number in enc. 2 so it is predator.
Ans:4
[quote=\"Jamesbond\"]http://i62.tinypic.com/2h85rnd.jpg\">

Thx for ur answer....by mistake I posted in P5 Science instead of P6 Science....shows I am stressed out :frustrated: :lightrod:[/quote]Thats fine..Good luck to your child...I think he is giving PSLE this year ?!

[Jamesbond]

I am the one giving psle. :rotflmao: :siam:

[janice_0950]

janice_0950:

Dear Science Expert,

please help.......... sob! sob! sob!


Test papper
Question.10
http://s256.photobucket.com/user/disneyterris/media/1_edited-1.jpg.html
(answer sheet: No.2)

Question.21
http://s256.photobucket.com/user/disneyterris/media/2_edit4ed.jpg.html
(answer sheet: No.3)

Question.34 a & b
http://s256.photobucket.com/user/disneyterris/media/3_edited-1.jpg.html

(answer sheet 34b):1 sibling


Thank you in advance!

Hi jojoberry, Thank you for explaination & helped.
:thankyou:

[sembgal]

jojoberry:

janice_0950:

Dear Science Expert,

please help.......... sob! sob! sob!


Test papper
Question.10
http://s256.photobucket.com/user/disneyterris/media/1_edited-1.jpg.html
(answer sheet: No.2)

Seeds cannot move! so No 3 cannot be the answer. Should be \"Shoots\" grow towards sunlight.

Refer to the Science textbook. Roots grow downwards. Shoot grows upwards.

[janice_0950]

sembgal:

jojoberry:

[quote=\"janice_0950\"]Dear Science Expert,

please help.......... sob! sob! sob!


Test papper
Question.10
http://s256.photobucket.com/user/disneyterris/media/1_edited-1.jpg.html
(answer sheet: No.2)

Seeds cannot move! so No 3 cannot be the answer. Should be \"Shoots\" grow towards sunlight.

thank you & noted!

Refer to the Science textbook. Roots grow downwards. Shoot grows upwards.[/quote]