Next, let’s learn about the relationship between voltage, current, and resistance with Ohm’s Law. This should lay the foundation of understanding the basic terms needed to start solving circuits. It’s the combination that creates the power. Or water spilling out of a cup on a table may have flow but there’s no potential behind it to do any work. Much like a raindrop falling won’t create a usable amount of power, a huge voltage without any current won’t produce much power. But if you have too little of one or the other, there isn’t much power. Or you can have a very large flow from a relatively low height create a lot of power. Going back to the water analogy, you can have a small flow from a great height produce a lot of power. But, given equal physical sizes, the battery can lift a box a total of 5,000 feet before running out of energy but a capacitor can lift a box a total of 300 feet before running out of energy.”Įlectric power, mathematically, is simply current times voltage, so is a factor of both flow and potential. Expanding on the box example and using some arbitrarily chosen numbers, what this means is that a capacitor can lift a box 100 feet in the air in one second, while a battery the same physical size can only lift a box 10 feet in the air in one second. “Batteries are more energy dense than capacitors but capacitors are more power dense than batteries. It may be 10 volts from the top to the bottom, but it’s also -10 volts from the bottom to the top, so v ab = -v ba. It makes even more sense when you realize that, since everything is relative, you can flip your perspective and invert the sign of the voltage. It may seem odd to do that sometimes but once you get some experience with circuits and electricity, negative voltages make a lot of sense. But then sometimes you get negative voltages, which just means that the electric potential at that point is below what we established as our “ground” potential. We typically assume that the lowest point is “0” or what we call “ground” as a reference. Turning this concept around, work can be defined as the voltage between the two points times the charged that was moved between them: W VQ We can use these concepts to derive a very important formula for guitar amplifiers. To do this, lets look at our Ohms Triangle.
![voltage and current to work done time voltage and current to work done time](https://adamcap.com/wp-content/uploads/2012/09/resistor-10-640x582.png)
We can use the known Amps and Volts to get our Resistor value. which gives us the most convenient definition of power for electric circuits, power voltage multiplied by current. It is the same with voltage - when we talk about voltage, we’re talking about the electric potential between two points in relation to each other. Our practice circuit to get a taste of Ohms Law. But what if we dug a hole at the bottom of the hill and made the bottom even lower? Or what if there were a mountain next to the hill? The hill is lower than the mountain, so there is a potential between the mountain and the hill, much as the bottom of the hill is a higher potential than a hole dug at the bottom. For example, the top of the hill is obviously higher than the bottom of the hill. The change in voltage is defined as the work done per unit charge, so it can be in general calculated from the electric field by calculating the work done against the electric field.One final thing about voltage - note that difference between one potential and another is relative.
![voltage and current to work done time voltage and current to work done time](https://image.slidesharecdn.com/equationsheetinternet-100224171544-phpapp01/95/equation-sheet-1-728.jpg)
In the more general case where the electric field and angle can be changing, the expression must be generalized to a line integral: More detail on variable field If the distance moved, d, is not in the direction of the electric field, the work expression involves the scalar product: In the case of constant electric field when the movement is directly against the field, this can be written The change in voltage is defined as the work done per unit charge against the electric field. HyperPhysics***** Electricity and Magnetism
![voltage and current to work done time voltage and current to work done time](https://image.slidesharecdn.com/lec4workpowerenergy-150127073027-conversion-gate01/95/work-power-and-energy-10-638.jpg)
This association is the reminder of many often-used relationships: More general case voltage: The potential difference between two points in a. The electric field is by definition the force per unit charge, so that multiplying the field times the plate separation gives the work per unit charge, which is by definition the change in voltage. This is true for many materials, over a wide range of voltages and currents, and the resistance and conductance of electronic components made from these. If one of the light bulbs is removed, the circuit is broken and none of the other lights will work. Work Done by Electric field Work and Voltage: Constant Electric Field The case of a constant electricfield, as between charged parallelplate conductors, is a good exampleof the relationship between workand voltage. Electrical Power is the product of the two quantities, Voltage and Current and so can be defined as the rate at which work is performed in expending energy.