Engineering Prep

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Sample Problem

EIT Certification Heat Transfer

Cooling a CPU


A square silicon chip (k = 150 W/m∙K) is of width w = 7 mm on a side and of thickness t = 2 mm. The chip is mounted in a substrate such that its side and back surfaces are insulated, while the front surface is exposed to a coolant. If 60 W are being dissipated in circuits mounted to the back surface of the chip, what is the steady-state temperature difference between back and front surfaces?


Fourier's law:

P=q=kAΔTtP=q=kA\frac{\Delta T}{t}


Assumptions: (1) Steady state conditions, (2) Constant properties, (3) Uniform heat dissipation, (4) Negligible heat loss from back and sides, (5) One-dimensional conduction chip.

All the electrical power dissipated at the chip's back surface is transferred by conduction. From Fourier's law:

P=q=kAΔTtP=q=kA\frac{\Delta T}{t}

Rearranging the formula to solve for the temperature difference:

ΔT=tPkw2=0.002m60W150W/mK(0.007m)2=16.33K\Delta T=\frac{t\cdot P}{kw^{2}}=\frac{0.002m\cdot 60W}{150W/m\cdot K(0.007m)^{2}}=16.33K

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Hi, I'm Kevin!

Mechanical Engineer based in Los Angeles, California. 10+ years of combined experience across multiple Fortune 100 companies, designing and building fighter/commercial jets, nuclear missiles, robots, classified weapon systems, NASA space vehicles, and more!

I'll be your instructor for this small passion project of mine. Always found the lack of MechE interview prep resources frustrating, especially compared to our coding counterparts. So, I created this centralized solution to practice for my own technical interviews, and to continually refresh the undergrad fundamentals that aren't always used while in industry. ¯\_(ツ)_/¯

Figured others could benefit, so please join me! No strings attached, seriously. I just enjoy optimizing designs/processes, building products, & trying new things :)



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Seamless, simple tool designed to encourage consistent and manageable practice daily. No need to set reminders, determine a study plan, or visit additional apps/websites - everything is automatically sent to your existing email. It integrates with your schedule with customizable email settings. A little build up every day prevents cramming towards the end! It's 100% free, and you can opt-out anytime.


How is this free when everyone else charges?

As a fun side project to learn new technologies, I built this tool to address gaps in my own interview prep process. Between working full time towards professional goals, commuting in LA traffic, and enjoying life as a young adult, I found the system filled with friction and obstacles. Now, I spend 10-20 min during lunch, between meetings (sometimes during), or just before bed, effortlessly studying months in advance. The motivation has been transformative, so I'm releasing it to the world so others can hopefully benefit.

Fortunately, I'm fully employed and can cover the monthly infrastructure costs. If you appreciate the work and want to support, feel free to buy me a coffee!


Does this service cover other engineering disciplines?

Due to my limited resources, the current scope of work only covers mechanical engineering topics, since that is my degree and profession. I'm hoping to expand the platform in the near future to include other disciplines. Sign up for this separate newsletter to be notified about upcoming product updates.