# What is Volatage: Definition and 19 Discussions

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1. ### Understanding Fundamentals of Electronics: Solving an Electric Charge Problem

It's not a homework. I came up with this problem myself. Trying to understand fundamentals of electronics. Do you know how to solve it? Is voltage somehow related to electron energy levels? What knowledge should I gain to be able to solve problems like that? Thank you! If we ground the cathode...
2. ### Relations between ##k## Currents & Voltages for Black-Box Device

Hi, I'm aware it is an odd question. Consider a ##k##-terminal electrical device as black-box. We know from KLC and KLV that just ##k-1## currents and ##k-1## voltages are actually independent (descriptive currents and voltages). Furthermore we generally expect there exist ##k-1## relations...
3. ### Batteries: Is the current a diffusion current?

Greetings, I realized that I don't understand a fundamental fact of common Li-ion batteries. During the charging process, electrons are forcefully extracted from the cathode and pushed into the anode. Charge balance then yields a flow of positive Li ions from the cathode to the anode (through...
4. ### Why does voltage = energy/charge?

When you say ##i = \frac{dq}{dt}## it makes sense since current is the flow of charge over time. But why was voltage defined as ##v = \frac{dw}{dq}## ? What made physicians define it in this way? Is there a mathematical way that can lead to this definition or did they define voltage just on the...
5. ### Help with NEXT and FEXT volatage magnitudes

Homework Statement A transmission line is formed by two identical parallel tracks in a printed circuit board. The line has a length of 50 mm and all line terminations are of 70 Ω. The line can be assumed to be lossless. calculate the magnitude of the NEXT and FEXT voltages generated in the...
6. ### Understanding voltage dividers

Hi! I'm working on a project in which a small microcontroller with a max. analog input of 5v takes readings from multiple sensors. I would like to make this input window a bit more versatile, and turned to voltage dividers as a solution. 'Problem is, I'm having a bit of trouble understanding how...
7. ### Trouble understanding common-emitter amplifiers

Hi there! I've been tinkering with some homemade speakers, and wanted to make a simple amplifier circuit to step up the some 3 volts that comes out of an aux jack to 9 or 10 volts. I decided that the common-emitter model looked the easiest to understand. I was mistaken. This is the simplest...
8. ### Voltage across two different circuits

I have a question regarding the voltage of two different circuits. In the first circuit there is a 75 volt battery with just one 4 ohm resistor. In a separate second circuit there is a 75 volt battery again, but this time there is a 4 ohm resistor and 9 ohm resistor in series. My question is...
9. ### Irrelevance of electrical potential

In regards to voltage and electrical potential, I have a question. I understand the voltage to be the difference in electrical potential of two separate points. So in an analogy am I correct to compare this to a bowling ball being 4 feet off the ground. So the bowling ball has a gravitational...
10. ### Understanding Cylindrical Capacitors: Charged vs. Disconnected

Homework Statement Normally this style of question wouldn't be too bad, however the 2 different parts confused me. Surely once set to a potential V, it would stay at that potential - it doesn't need to stay connected How are the 2 parts any different from each other?
11. ### Detect increasing or decreasing pot output

I want to detect whether potentiometer output voltage is increasing or decreasing and convert this to a digital signal. the circuit must be able to sense tiny voltage changes (order of 10mV) and with high speed. all I am interested is if Vout increases or decreases not by how much increasing V...
12. ### Two thermophores boiling water

Homework Statement We are given two identical thermophores. It is known that one of them can boil a liter of water in t = 600 s. How much time would it take to boil one liter of water if we used two of these thermophores, connected a) in a series circuit b) in a parallel circuit Voltage: 230 V...
13. ### How Does Increasing Voltage Reduce Power Loss in Electrical Transmission?

Homework Statement A power station delivers 750 kW of power at 12,000 V to a factory through wires with total resistance 3 Ohm. How much less power is wasted if the electricity is delivered at 50,000 V rather than 12,000 V? Homework Equations P=I x V, P= V^2/R, P=I^2 x R The Attempt at a...
14. ### Differences between two Voltage formulas

What is the differences between these two voltage formulas. 1. for a point charge: $$V = k\frac{q}{r}$$ 2. for an inductor: $$V(t)= L\frac{di}{dt}$$ Why are there different voltage formulas? Can second one be derived from the first one? Or do they completely represent different concepts?
15. ### Voltage change to go from 60-W to 50-W?

In a "brownout" situation, the voltage supplied by the electric company falls. Assuming the percent drop is small, show that the power output of a given appliance falls by approximately twice that percent (assuming resistance does not change). How much of a voltage drop does it take for a 60-W...
16. ### Alternate to a proportional linear solenoid

I am trying to build a circuit using gears, motors, and relays only which mimics the motion of a proportional linear solenoid i.e. Hold a spring compressed at a certain distance depending on the current passed, and push/ release it further based on the increase/ decrease of current. (V=12 V...
17. W

### Understanding Voltage Dividers: A Practical Approach

*sigh* voltage divider...? I've been going over basic circuitry and got to the voltage divider. I don't understand the proof here: http://en.wikipedia.org/wiki/Voltage_divider#General_case The first line makes sense. From Vi to Ground there are two resistors in series, so you add them...
18. ### What is the formula to solve for RPM to volatage output in a generator

can anyone tell me how to solve for the voltage output in a generator and all the variables needed to solve it. What if I only have the RPM can I solve it? thanks
19. ### Does Voltage Change When Resistance Drops in a Series Circuit?

if i have two components in a series circuit and the resistance across one drops, does the pd across the other one increase?