Nuklear said:
ALl of you are kind of contradicting or CHroot is. He's sayign the voltage of the battery does drop.
Well, your original question was pretty hard to understand. We're all correct, in our own ways. The battery's open-circuit voltage never changes, it's dependent only on its chemistry. The battery's voltage
does change under load, but typically only by a very small amount. The battery manufacturers go to great lengths to minimize the internal series resistance. An
ideal battery has no internal resistance at all, and its voltage never changes. In most applications, you can completely ignore the very small changes in a battery's voltage due to load.
There are devices where the voltage varies. Take radios. Yo can change the volume. SO as the volume increases is the voltage of the battery increasing or is it somewhere in the circuit? IS a battery always putting at it's max output?
No, the battery is not changing at all -- it's always producing [essentially] the same emf, or voltage. When you turn the radio up, you're changing the gain on the amplifier, and the amplifier consequently consumes more power, which it sends to the speakers to make them produce louder sounds. Since the radio's supply voltage is constant (the battery does not change its voltage), it draws more
current from the battery.
The formula we learned for voltage is Potential Energy over Coloums equals voltage. basically it's energy per COloumb. I'm beginning to see it doesn't matter how many Coloumbs are in the wire, just that are flowing by the battery per second...current. NOw just off a but, do all wires have the same amount of ELectron-Coloumbs inthem?
A specific volume of, say, copper has a specific number of atoms in it. Each atom has a specific number of electrons, so you can figure out how many electrons are in a chunk of copper. This is not very important for the study of electronics, though -- we're concerned with the
movement of electrons, not the number of electrons initially in the wire.
Consider a garden hose -- you don't really care how much water exists in the hose, and inside the pipes in your house, and in the pipes that bring water from the city water supply into your house. All your really care about is how much water comes out of your hose per unit time, so you can water your lawn.
ANd in Home power, does the current vary whenever you turn on a light, device, or appliance? If there's a set voltage and current coming into your house while you've got the TV,Microwave,lights, and radio on and then you switch on the washing machine do the other appliances loose volts? If not, how do they keep the wattage stable throught the houses wiring?
Indeed, turning on appliances means you're drawing more current from your house's electrical supply. If you go look at your meter, you'll see its disc spinning more rapidly. The meter is not much more than an ammeter (current meter).
If the electrical transmission system were made out of ideal wires (with no resistance), your electrical supply would maintain the same voltage (120VAC, for example), regardless of the load you put on it. The voltage would be rock-solid, all the time.
In the real world, wires and transformers and other devices in the transmission system do have resistance, and do drop some voltage. Consider a very poor length of wire with 1 ohm of resistance -- when you pass one ampere of current through it, it loses 1 volt of emf from one end to the other. It's a small effect, considering one volt out of 120 is rather insignificant, but it's a real effect.
This is why your lights will flicker or dim when your air conditioning unit turns on: the AC motor pulls a very large amount of "in-rush" current as it turns on, and this large current causes your entire house's electrical supply (which has some small, but non-zero resistance) to drop a few volts for a couple of thousands of a second.
- Warren
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