Q&A - PSLE Science

[joconde]

Hi, can anyone explain to me why option (1) is the correct answer :


http://www.postimage.org/image.php?v=Pqcg4kJ

I had thought that bulbs in parallel are suppose to draw more power from the battery. Thus, bulb Y should be dimmer after bulb Z is added. No ?

[Nebbermind]

joconde:

Hi, can anyone explain to me why option (1) is the correct answer :


http://www.postimage.org/image.php?v=Pqcg4kJ

I had thought that bulbs in parallel are suppose to draw more power from the battery. Thus, bulb Y should be dimmer after bulb Z is added. No ?

is this a acs revision paper?

from an engineer pov, Y shd be brighter coz when X//Z, the overall resistance is lower than before so more current will go thru Y.
But since this is P6, I'm not sure :oops:

[Sun_2010]

Nebbermind:

from an engineer pov, Y shd be brighter coz when X//Z, the overall resistance is lower than before so more current will go thru Y.
But since this is P6, I'm not sure :oops:

Exactly.

Joconde, the brightness of a bulb depends on the electric current flowing thru it. If more power is drawn the batteries will run out faster .

So I think unless a resistance(say bulb) is added in series there bulb Y wont get dimmer .

[joconde]

Nebbermind:

joconde:

Hi, can anyone explain to me why option (1) is the correct answer :


http://www.postimage.org/image.php?v=Pqcg4kJ

I had thought that bulbs in parallel are suppose to draw more power from the battery. Thus, bulb Y should be dimmer after bulb Z is added. No ?

is this a acs revision paper?

from an engineer pov, Y shd be brighter coz when X//Z, the overall resistance is lower than before so more current will go thru Y.
But since this is P6, I'm not sure :oops:

it's rosyth 09 prelim. ur engineer's theory very cheem lei. from my layman's point of view, it's more load added, so Y should be either dimmer or at most as bright.....v confused :?

[joconde]

Sun_2010:

Nebbermind:

from an engineer pov, Y shd be brighter coz when X//Z, the overall resistance is lower than before so more current will go thru Y.
But since this is P6, I'm not sure :oops:

Exactly.

Joconde, the brightness of a bulb depends on the electric current flowing thru it. If more power is drawn the batteries will run out faster .

So I think unless a resistance(say bulb) is added in series there bulb Y wont get dimmer .

Hi sun_2010, so you mean since the electric current flowing thru Y is the same, it will shine as brightly as before ? Adding Z will only cause the batteries to run out faster, but will not affect the amount of current flowing thru Y, is that ur point ?

Makes some sense to me now...

[Sun_2010]

Joconde,


you could look at it that way.

Like Nebbermind wrote, actutally the current flowing in second case is higher , but this is definetely beyond P6 syllabus.

btw is it this yr prelim paper?

[joconde]

Sun_2010:

Joconde,


you could look at it that way.

Like Nebbermind wrote, actutally the current flowing in second case is higher , but this is definetely beyond P6 syllabus.

btw is it this yr prelim paper?

Thanks sun_2010 and nebbermind for clearing my doubts.

It's Rosyth 2009 Prelim paper, from the Jeremy's stack of prelim papers I bought.

[Dharma]

joconde:

Sun_2010:

Joconde,


you could look at it that way.

Like Nebbermind wrote, actutally the current flowing in second case is higher , but this is definetely beyond P6 syllabus.

btw is it this yr prelim paper?

Thanks sun_2010 and nebbermind for clearing my doubts.

It's Rosyth 2009 Prelim paper, from the Jeremy's stack of prelim papers I bought.

http://www.physicsclassroom.com/Class/circuits/u9l4b.cfm may be helpful

[tianzhu]

Hi


I hope I am referring to the right question, Q15 from Rosyth SA2 2009.I cannot read images from postimage as Internet Security 2010 would warn of security risks.
http://test-paper.info/filemgmt/viewcat.php?cid=117

This question involves a combination of series and parallel circuits which may be beyond P6 scope.

I was referring to the PSLE science guide (MC, old edition) and found that students learned about addition of bulbs in either series or parallel circuits. It appears that a combination circuit is not covered.

The correct answer is option (4).Bulb Y is brighter than before.

This brings us to the next question, students may be curious to find out what happens to the brightness of bulb X after the addition of bulb Z. Is it brighter or dimmer than before? Give it a try after your PSLE.

Best wishes

[baibai06]

Muffins:

baibai06:

Hi........

i am about to take PSLE this year

i came across a question showing a fish tank with a fish and hydrilla and the fish tank is placed
in sunlight, but yet the fish died after 12hours or so during the night that day....
the fish were given no food.....
so can we say that the fish ate the plants, and therefore there were no more plants that photosynthesised and produced oxygen, there the fish died due to a
lack of oxygen?

i heard that it was not reconmmended to say that fish ate the plants.....
can anyone clarify about that?
thanks :?

Ah... Here is the clue. It died during the night. In the night the plant would only respire, thus taking in too much oxygen, so the fish and the plant would have to compete for air. In the end, the fish died due to too little air being taken in by it....

thanks......
now i understand