Evan Toh
2010SPP2Q12 Fuel gauge using variable resistor
Solutions: As the fuel level drops, the float which stays on the fuel surface will descend. The rod which is attached to the float will...
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Evan Toh
Oct 211 min read
Using P = I^2R and P = V^2/R to explain which component uses the highest power or energy.
Instead of P = IV to explain, it might be easier to explain using P = I^2R when the components are connected in series where current I is...
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Evan Toh
Oct 211 min read
When a thermistor is connected in series with a fixed resistor, how to explain the p.d. varies as resistance temperature changes?
When two components are connected in series, where one is a fixed resistor and the resistance of the other can vary (e.g. thermistor,...
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Evan Toh
Jan 11 min read
2010SPp1q12 Lens - focal length definition
Answer: Option C Focal length f is the distance between the focal point and the centre of the lens (optical centre) . Note that only...
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Evan Toh
Dec 31, 20231 min read
Which is better to cool the food? Copper or ice at 0oC - 2008SPP2Q6(b)
Other examples in our daily lives: In some supermarket, the seafood are placed outside of air-conditioned place. The seafood is kept cold...
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Evan Toh
Dec 31, 20232 min read
SP N2007 P1 Q16 – Which events will cause the fuse to blow?
An electric cable contains three wires live, neutral and earth. The cable is correctly wired to a plug which contains a 3A fuse. The...
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Evan Toh
Dec 31, 20231 min read
Identifying what lens, focal length and image from 2 rays – PP2010P1Q23 and SP2014P1Q11
These 2 questions are actually the same. Q23 is from 2010 Pure Physics P1 while Q11 is from 2014 Sci Physics P1. Take a look at these 2...
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Evan Toh
Dec 31, 20231 min read
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Evan Toh
Dec 31, 20231 min read
2013SPp1q17 What is the new P when V across resistor is doubled? Similar 2018PPp1q31
Answer: Option C View the videos below to learn how to solve it. There are more than one method. Alternatively, you may put values to...
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Evan Toh
Nov 30, 20231 min read
N2007P1Q9 Pure Physics – Energy needed to pump water up a building
Answer: Option B Since water will naturally reach 40m high from the bottom of the apartment, you only need to pump the water up by a...
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Evan Toh
Nov 30, 20231 min read
2004PPp1q4 2010SPp1q4 Dynamics (3rd law)
Answer: Option D Key concept here is Newton’s 3rd Law. Action equals reaction. Both trolleys are connected by the spring, hence the...
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