Q&A - PSLE Science

[chrisu]

Yes answer is No.1 Bulb X will not light up.

We assume both batteries are identical thus the charges cancel one another. But if there are 3 identical batteries (arrange like +-+--+ or -+-++-), then the bulb will be lighted up dimly.

In the diagram, the batteries are arranged in -++-, so it cancel each other and bulb will not light up.

Hope it's clear.

vidhyalog:

Atutor and others - sincere thanks upfront for answering these queries. I have 3 more queries.

1) ACS prelim 2011. The following circuit is in parallel arrangement - answer is No 1. But why? http://i54.tinypic.com/28khahx.jpg\">

[atutor2001]

Hi vidhyalog


2) ..... - we were wondering if it is due to the word immediately - he then reasoned that for the first instant the flask will expand - that would provide more space for the air in the flask, which would lead the ink to move leftwards. Firstly is the answer (2) - and if it is - is his reasoning correct?

I fully agree with the above reasoning.

3)My son answered (1). Answer key is (2). But he argues that we cannot assume that layer of oil and cover will prevent evaporation at the same rate - there may be differences there. So he will not choose Set-up D as a fair test.

I will also not choose set-up D.

[Alchemist]

:thankyou:

[Nebbermind]

I thought the bigger vol of air in X will push the ink to Y? Isn't it (1)? :?

[Alchemist]

Nebbermind:

I thought the bigger vol of air in X will push the ink to Y? Isn't it (1)? :?

Hi Nebbermind

That's what he answered first and I thought too. But then why is there the word \"immediately\". Because 2 things happen - at first - flask expands - and as air occupies space - the air in the flask will occupy the expanded space there causing the ink to momentary move towards X - before the air in X expands and therefore pushes it to the right.

This reasoning was given by my son when he noticed the answer he wrote was wrong. He then guessed it is because of the word immediately.

I find it quite sad that some questions may trip up children who can understand concepts - but are not so careful. But that is life I guess - you should know the concepts and be super-careful in reading the question.

[Nebbermind]

yup, knowing the facts is not enough for psle science. need to know what the qn is asking for.

when my boy 1st attempted those past yr qns, think he scored like 60% or so. Only after the 'cher had gone thru the revision and taught them how to interprete the qns, then he started doing better. Think for science, cannot just hamtam the 1st thing that come to the mind. must calmly dissect and analysis the qns before coming up with the answers.

[P5G]

44. The diagrams below show two different power stations A and B.


power station A - Fire heating up a container of water, the container is connected to a turbine which is connected to a generator.

power station B - Water in a dam, flowing into a turbine, connected to a generator.

The diagram below shows the energy conversions that takes place in the two power stations.

Potential energy –> Kinetic energy –> Kinetic energy [turbine] –> Energy X (generator) –> Energy Y (generator)

a) Identify energy X and energy Y.
Energy X __________
Energy Y __________


TIA.

[Verysuperkiasu]

atutor2001:

Anyway, my answer to such a question would be :

For P4 :
It is not a light source because it cannot produce (don't use emit) on its own as the light emitted by the bulb is produced by the electric current flowing through the bulb.

For P6 :
It is not a light source because it cannot produce (don't use emit) on its own as the light emitted by the bulb is converted from electrical energy that is supplied to the bulb by batteries or other power sources.

Thanks!

[Verysuperkiasu]

When heat is applied to a solid and a liquid of the same substance which expand more ? _____________

[atutor2001]

P5G:

Potential energy --> Kinetic energy --> Kinetic energy [turbine] --> Energy X (generator) --> Energy Y (generator)

a) Identify energy X and energy Y.
Energy X __________
Energy Y __________


TIA.

X should be kinetic energy and Y should be electrical energy.

Kinetic energy of the turbine is transferred to the generator.

The kinetic energy causes the coils in the generator to turn which will then be converted to electrical energy.