Question

What's Voltage exactly?!! I know that it's the electric potential to move charges from A to B. but what does it mean when they say "voltage at resistor R" don't they need TWO points to determine voltage?!

Answer 1

and what do they mean when they say voltage of an object?!!!

Answer 2

ok man basically it is energy consumed per unit charge by an object

Answer 3

yeah that's the formal definition...can u explain a little bit plz....who could u say voltage at a certain point when you actually need TWO points to measure it??

Answer 4

salamon firstly to tell u i have started my second semester only :P and yehh suppose we have two points a & b , then measuring across it means that how much energy loss has taken place from point a to b

Answer 5

it's all just so confusing @.@ lol...I have a circuits quiz tomoroz an i have no idea what voltage is :DDD

Answer 6

men questions like this are not being asked like what is voltage :P

Answer 7

You are right; voltage is always defined in the lumped parameter model we're using in the course as between two points. But it's awkward to always say "the voltage difference between point A and point B", so people often just define some point in the circuit as "ground" or "0V". Then when they say "the voltage at point A" it's really just syntactic sugar for saying "the voltage at point A with respect to that point over there with the ground symbol". Sometimes people get even lazier and don't write the ground symbol if there's just one power source for the circuit -- they assume it's at the negative side of the power source. They're wrong; they should explicitly write in the ground symbol.

Answer 8

salamon you actually need the two points its like the physics definition of work, you need a displacement, you know going from A to B, if there's no distance travelled even though there was a force trying to move an object it may not be enough to produce a displacement (no work though a force was there) , but going back to electrical terms, this implies moving a charge unit or coulomb from one terminal to the other through the element against the electrical field. Also if there's no resistance (ideal wire) we have no oposing force and thus no voltage across the ideal wire.

Answer 9

In Spanish the term is "Trabajo" I literally translated to "work" I hope it's alright :)

Answer 10

Yes, it is true . voltage at a point means it is with respect to the 'ground' or '0v' potential. practically when we measure the potential at any point on circuit we keep the red probe at the required point and the black probe at the ground terminal of circuit. if no ground terminal exixts we keep the black probe of multimeter at the negeative terminal of the battery. Theoritically even i we define the potential at a point it is nothing but the potential of that point with respect to a point at infinite distance(where the potential due to source charge is asumed to be zero.)

Answer 11

The voltage across a resistor as a result of current flowing through the resistor (E=IR) is sometimes referred to as "voltage drop" or IR drop. good luck on the quiz!

Answer 12

@junglejim great answer...thx so much for your help guys ^.^