First three terms of a GP
Category: Q&A
Solve for z
Parametric equations curve C
vector equation of a reflected line
Heat Sinks
a(i) Copper (or any metal).
Copper, being a metal, is a good conductor of heat. The heat generated by the electronic component will be conducted away at a faster rate by the heat sink, preventing the component from overheating.
ii) Black color.
Black colored surfaces are better emitter of radiant heat than bright colored surfaces. This will help the heat sink to emit its heat to the surroundings at a faster rate, so that the heat sink do not get too hot, and will still be able to gain heat from the electronic component effectively.
b)(i) 1W –> increase by 2 deg C
so 10W –> increase by 20 deg C
Answer: 20 deg C
b)(ii) As the temperature of the heat sink increase, the rate of heat conduction from electronic component will slow down, and the rate of heat radiated to surroundings will increase. Eventually, the rate of heat conducted into the heat sink will be equal to the rate of heat emitted from it. At this point, its temperature will remain constant.
force on a wire XY
a) The force on XY is acting downwards.
Applying Fleming’s Left Hand Rule, the middle finger points into the page, in the direction of the current flow from X to Y, the index finger points to the right, in the direction of the magnetic field, the thumb will be pointing downwards, which represents the direction of the force on XY.
b) (i) Pan moves upwards.
b) (ii) When the magnets are brought closer together, the magnetic field strength of the magnet increases, increasing downwards force on XY. The greater clockwise moment will then cause the pan to tilt upwards.
c) (i) When an alternating current flows through the iron bar, a rate of change of magnetic field is produced by the iron bar. The rate of change of magnetic field produced an induced electromotive force in the flat coil, and hence an induced current flow through the closed circuit of the coil, causing the lamp to light up.
c) (ii) The lamp will be dimmer.
The lower frequency produced a lower rate of change of magnetic field, which produce a lower electromotive force in the flat coil, causing the voltage supplied to lamp to decrease.
ratio theorem involving triangles again
Click on the title of this posting to see the question and worked solution.
One of my students told me a similar vector question came out in this year’s A level P2.
Luckily we went through this question one day before the paper. Yeah!
An alternative method to solve the question is also provided.
Machine Codes
Click on the title of this posting to see the question and worked solution.
Many students have problems with solving part (iii) of the question.
It is easier to solve with the aid of a Venn Diagram. Once the required region is identified, think of the possible events that can occur within that region, and come out with the required probabilities. If you are still having problems, whatsapp me! 🙂