- An incandescent light bulb can be modeled as a resistor. The CFL and LED light bulbs show much complicated voltage-current characteristics. They cannot be modeled using resistors, capacitors and inductors.
- This video shows how the dimmer switch affects the sine wave. Note that the wave is changed even when the switch is set at full power. This is the reason why compact florescent lights won’t work with dimmer switches.
- Piezoelectric materials such as lead zirconate titanate (also called PZT) can be used both as a sensor and as an actuator. The novel feature of this video is that no power amplifier is used; the PZT is driven by a function generator alone.
- Friction enables a “Trojan horse” with internal moving parts to creep along the floor.
- Patterns form by particles on a vibrating table.
- Predicting the wave response to perioric excitation can be too difficult.
- This video shows parametric instability in a mechanical system
- This video shows hysteresis in the dynamic responses of a nonlinear system
- This video shows internal resonances between modes. The internal resonance is strongest when the natural frequency of the bouncing mode is nearly twice of the swing mode.
Do It Yourself
- Your gas fireplace works during power outage except the blower. Thermopiles heated by the pilot fire generate enough electricity to operate the millivolt gas valve. I assume my gas water heater works in a similar way.
- When repeated jump starts fail, the starter is often the suspect. Occasionally, the defective battery develops internal electric short to prevent jump start. Disconnect one of the battery terminals and try to jump start again before replacing the starter.
- My refrigerator stopped cooling suddenly. Defrosting water spills on the floor. Clicking noise can often be heard. Saw several internet posts on “Defrost Timer” problem. After talking to a few of my friends, I concluded that the “Overload Relay” should be the first thing to check.