Category Archives: Physics

Directly downwind faster than the wind

Is it possible to build a wind-powered vehicle that can continuously travel faster than the wind, in the same direction as the wind? Like the airplane-on-treadmill problem and the Feynman sprinkler problem, this question has spawned endless Internet arguments. Continue reading

Posted in Physics | Leave a comment

Electromagnetic radiation from accelerating charges

Electromagnetic radiation is something that has often eluded my intuition. Electrical engineering depends on numerous abstractions: current flowing in wires like a fluid, capacitance/inductance in lieu of near field interactions, antenna theory to model far field interactions, etc. These abstractions … Continue reading

Posted in Physics | Leave a comment

MEMS oscillator frequency increase from helium

You may have heard of the incident where a helium leak suddenly disabled many iPhones at a medical facility. The root cause — tiny MEMS oscillators being susceptible to helium leaking into their hermetically-sealed casings — is interesting but not … Continue reading

Posted in Physics | Leave a comment

H field and material boundaries

For a long time I thought of the H field as being generated by free currents only. The problem with this view is that it leads us to make erroneous assumptions. We know from the definition of H that:   … Continue reading

Posted in Physics | 2 Comments

Magnetic field of a ferrite core solenoid

Consider a solenoid made of wire wrapped around a rod made of iron, ferrite, or other ferromagnetic material: It is well known that the magnetic field will be significantly stronger inside such a solenoid, compared to an air core solenoid. … Continue reading

Posted in Physics | 5 Comments

Weather balloon physics

One of the simplest solutions for sending measurement instruments up into the stratosphere is a rubber balloon filled with hydrogen or helium. While the physics of such a balloon would seem to be simple, there are actually some interesting considerations.

Posted in Physics | 12 Comments