[The Twelfth Blog] Magnetism.

I wouldn't consider myself a very curious person, naturally, so I have probably never thought about it (although I don't think I would have noticed in the first place... :|), but after this lesson in physics, I know why so many different objects can be powered/charged by being plugged into wall outlets. It can't be that all objects require the same voltage, right? So there must be something that is able to convert the wall outlet's 120 volts into the proper voltage for each individual appliance... And this trusty tool is the AC adaptor! These are so common that many people probably don't even think about them. In fact, I'm making use of one right now, as I charge my laptop whilst writing this blog.


How it works: 
- Within the adaptor, there is a ferromagnetic core (say of iron) around which two coils (primary and secondary) are wound
- The primary coil receives the alternating current from the wall outlet, which creates an alternating magnetic flux 
- This alternating magnetic flux leads to a varying magnetic field in the iron core
- When the secondary coil is brought within the varying magnetic field, an alternating current is induced within it
- Since V₁/N₁ = V₂/N₂, V₂ is determined by the ratio of the primary coil's loops to the secondary coil's loops
- To reduce the voltage that leaves the adaptor, the secondary coil should be made of fewer loops accordingly


Well we sure do seem to learn new things every day, even things that we may never have thought about if not for physics class. :]

[The Eleventh Blog] Current Electricity.

I try not to turn on the lights in our house as often as possible, relying instead on the natural light from outside (my mother is not very approving of this, but that doesn’t stop me... :P). However, when it’s rainy and the sky is gray, or when I’m up studying in the wee hours of the night, the lights become necessary. In my room, I have a light fixture above my bed that looks like this:

[It’s kind of ironic how nice the plants look behind my window, since it has basically
been raining the entire day. Not the best weather to motivate me to do my homework. -.-]

As they are, the lights seem to be in series. However, the circuit that they are a part of is actually in parallel. Which is good, because a parallel circuit is much more efficient than a series circuit. In a series circuit, when one bulb goes out, the others go out too, because the current can no longer flow through the entire circuit. But since my lights are wired in parallel, even if one bulb goes out, current still continues to flow to the other bulbs to keep them lit. Also, the total resistance of the circuit is much lower in a parallel circuit than it would be in a series circuit, allowing more current to flow through it. In a series circuit,  R_total = R₁ + R₂ + R₃, while in parallel, 1/R_total = 1/R₁ + 1/R₂ + 1/R₃. Lastly, the bulbs will shine brighter in a parallel circuit than in series. In series, the voltage is split between the bulbs, whereas in parallel, (theoretically) all the voltage supplied by the source goes to each branch of the circuit. Since power can be defined as P = V²/R and the voltage supplied to each bulb in a parallel circuit is greater than that supplied in a series circuit, the bulbs in parallel will be brighter.