Induction chargers

My brother has a little blue creature that glows, and you charge it by placing it on the little charging dock. I always wondered how this worked, since there are no plugs or contacts that connect the charging platform to the light. Now I know that it works through inducted current! The dock probably uses some kind of solenoid and the current from the outlet that it's plugged into to make a magnetic field. The outlet is 120 volts, and the potential difference in the charger itself is probably different, so this means that there are probably two solenoids forming a transformer. The magnetic field formed by the current flowing through the wires in the charger affects the circuit in the light itself and causes it to have a current flowing through it. Since the light charges, though, and doesn't go off as soon as it leaves the charger, some kind of capacitor or rechargable battery must also be part of the circuit so that it can store the charge for later use.

Circuit breaker!

This is the main breaker for the FRC robot! (Robotics is very useful for physics blogs..)
We use it for the on/off switch on the robot, but it's mainly meant to keep too much current from flowing through the circuit. If there is too much, the breaker heats up and switches the robot off. The little black part clicks out. To turn it back on (hopefully after you removed some of the motors and other things that are causing resistance) you click the black back in. Normally to turn off the robot you push the red button.

Naturally, you want to mount this breaker where it won't be hit by an errant ball, or your robot would randomly go dead, since the circuit would be broken and no current provided to the motors, speed controllers, and other parts.

I'm not sure why the picture has decided to be upside down, but I'm too lazy to fix it. :P The limit on this breaker is 120 amperes, so if it exceeds this limit the breaker will turn off.

On a random note... yay for working on robotics for over 9 hours straight and leaving school at 12:30 am!!!!

Whee...

Light bulbs!

In my bedroom, the lights in the fan are still normal incandescent light bulbs, rather than florescent. This is because the lights in my room can dim, and most florescent bulbs can't dim. As you can see, the filament is visible. Power = I * delta V, and also = delta V^2/R. The power that is lost can be calculated, if you knew the resistance of the material of the filament. The change in voltage is the same as the voltage of the light bulb, or 40 watts. This loss of power as the current passes through the wire is the energy that becomes the light that we see. This is why a light bulb with a higher voltage, such as 60 watts, is brighter, since the voltage is higher and the power lost will also be higher.