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Course: Electrical engineering > Unit 1
Lesson 1: Getting started- Electric current
- Current direction
- Voltage
- Conventional current direction
- Preparing to study electrical engineering on Khan Academy
- Basic electrical quantities: current, voltage, power
- Numbers in electrical engineering
- Defining the standard electrical units
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Voltage
Voltage is a cornerstone concept in electricity. We create an intuitive mental image by comparing voltage to gravity. Created by Willy McAllister.
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Wouldn't it be wiser to consider voltage as the difference of potential between 2 nodes? That's how it's taught in Engineering School at least.(33 votes)
The ski slope isn't a bad analogy for potential. The video makes an analogy between delta height and delta volts. It also implies the concept of ground potential.
IMHO the battery is backwards. There will be an unfortunate road bump when students must come to grips with the convention of current flowing from positive to negative...
Regards,
APD(5 votes)
From what I am seeing we would only need one battery so why do we have to replace them all the time.(20 votes)
The chemical inside of them that manages the difference evens out over time making it so there is no diffrence I think.(2 votes)
I don't like the mountain analogy, water analogy is better, with pressure, since in a circuit voltage doesn't depend that much on the length of the wire, rather on it's resistance, if say we find a wire with zero resistance and we hook it on a 20 volts battery, voltage will be 20 across any two points. Am I right ?(11 votes)- Hello again Feraru,
There is no such thing as a wire with zero resistance (assuming we avoid superconductors). But even then there would be resistance in the connections to the cryogenic parts.
Both analogies are a good starting point but they leave many questions unanswered especially when you start discussions of capacitors and instructors. In this video I present another way to view the situation. Please let me know what you think:
https://www.youtube.com/watch?v=XdgKqf4h0tQ
Regards,
APD(9 votes)
- Is my understanding correct by saying, "one volt is the energy required to move one coulomb of electrical charge", or is it
"One volt is the amount of work one coulomb of electrical charge can potentially do"?
Which one is correct?
Thanks!(3 votes)
The term "voltage" is the honorary name for "electric potential difference". If it takes 1 joule (J) of work to move a unit charge (1C) between two points in space, then the electric potential difference between those two points is 1 volt (V).
That means 1 volt = 1 joule per coulomb.
If you have to push on the 1C charge to make it move, that means YOU are doing the work (work = force x distance). If you release the 1C charge and it forces its way back to the starting point (like it flows through a circuit), then the CHARGE is doing work.
Here is a formal definition of voltage:
https://www.khanacademy.org/science/electrical-engineering/ee-electrostatics/modal/a/ee-electric-potential-voltage,
or this revised and improved version: https://spinningnumbers.org/a/electric-potential.html(6 votes)
- So then, according to the mountain analogy, higher the voltage, larger is the amount of work done=> magnitude of the current flowing through the circuit will be large. Am I right?(5 votes)
- Hello Madhushree,
Your statements are true provided we keep the resistance the same in both circuits.
Please watch these two videos I made to help explain this situation. If you still have questions please leave a comment below.
https://www.youtube.com/watch?v=XdgKqf4h0tQ
https://www.youtube.com/watch?v=d1AokT4-pC0&t
Regards,
APD(2 votes)
How is the voltage across a battery different from the voltage across a load?? im thinking it has something to do with power, i.e one supplies power and the other uses power.....ahhh im unsure. If someone could clarify would be much appreciated.(1 vote)- There's just one kind of voltage, it's called voltage. It's the number you see if you touch two points in a circuit with a voltmeter. A battery generates a voltage, and yes, it generates power. The term "load" refers to the thing connected to our circuit, the thing that we want to deliver power to. We say a load "dissipates" power. For example, the speaker or the earbud is the load for our radio or music player. In the simplest case, a resistor can be called a load. If we measure the voltage across a load we get a number. That number means the same thing as if we measure across a battery, it's the voltage between those two points.(9 votes)
I have learned about voltage in other classes but it was never explained this simply. Thank you(4 votes)
does higher voltage mean faster speed of electrons(4 votes)- Sign Convention: I understand that electrons will move around the circuit to the positive end and from your drawing, potential energy represents a high electrical presence.
My concern is that most electrical diagrams show positive, or conventional current flow as being the preferred electrical direction. Which is most favorable in our present world?(3 votes)- Never mind. Question answered in next video.(1 vote)
wait a battery is like a hill please help me under stand this(3 votes)
Video transcript
- [Voiceover] Voltage is one of the most important quantities
and ideas in electricity, and in this video we're gonna develop an intuitive feeling
for what voltage means. But it has to do with potential energy of electrical charges
and that's what we're going to cover here, we're
not gonna do a derivation, but we are going to do
an intuitive description of what voltage means. We're gonna start with
an analogy to gravity. Gravity and voltage are
really similar ideas. I'm going to draw a mountain here. Here's some mountain-side with snow on it. And I'm going to put a mass here, here's a mass of some mass M. And it was lifted up to the
top of the hill somehow, by a ski lift, by a mountain
climber, something like that. And if I put it on top of
the mountain and I let it go, the potential energy that it has is going to be dissipated as kinetic energy and that mass is going to
roll down the hill to here. And as it does, it could do some work. It could hit some trees,
let's draw a tree. And it could run into a tree
and knock that tree around. It could hit a bear, it
could bounce off rocks, all kinds of things, so that's
a mass rolling down a hill. Now if I draw, this is a
way to think about voltage, think about voltage as
being another mountaintop, and this time we'll put a battery in here. This is our battery, this is
what a battery does for us, it actually builds our mountain. The battery actually delivers electrons to the top of the hill, so
here's an electron coming out of the battery terminal,
the negative battery terminal. And if I release this, it is
going to roll down the hill. And eventually it's going to return to the bottom side of the battery. But the same thing, this
is the image you have in your head when we hook up a circuit. Along the way I could put in
different circuit components like resistors or capacitors
or anything like that, and I could make this electron do work and bump into things as it goes down. So, the amount of voltage here is proportional to the
height of this mountain. A high voltage is a high mountain and a low voltage is a low mountain. The electrons are pushed
out the top by the battery and roll down to the bottom
doing work along the way, and this is where we
do our circuit design. That's what we're doing over here, we buy batteries and we
do our circuit design and study over here. So this is a pretty good
analogy for thinking about voltage as you begin
to build your circuits. See you next time.