Physics Homepage


Voltage

Voltage is a little bit more complicated than current. If current is the flow of charges than an analogy would be he flow in a river. Voltage is analogous to what makes the river flow to begin with. In case of the river that would be a difference in altitude or a gradient or, in physics words, a difference in gravitational potential, That’s why voltage is sometimes called potential. A river can only flow if there is a potential difference, it flows from high potential (a lot of potential energy) to low potential (less potential energy).

 

Voltage

In a circuit the voltage, or potential difference, makes the current flow. The battery is what provides the voltage. It lifts the charges up to a higher energy level, and as the charges flow through the circuit they loose this energy as they do work inside the light bulb. The energy drops to a lower level inside any resistor. We call this the voltage drop (delta V). When charges flow through a wire they loose no (or more precisely very little) energy. We do want the charges to do work inside the wires, but they do as you have found out when you hooked the wire up to the battery directly – it got hot. In an ideal wire charges do no work, because ideal wires have no resistance, just like ideal batteries.

 

The voltage model is made up of two concepts that depend on how the light bulbs are hooked up in a circuit. In series, the voltage drops have to add to the voltage in the battery. If three identical light bulbs are hooked up in series to a 6 V battery, each of the light bulbs will get 2 V. If the light bulbs or resistors are not identical, the one with the greater resistance gets more voltage. Voltage (drop) and resistance are proportional.

The second concept that makes up the voltage model says that in parallel the voltage drop is the same for each resistor. This becomes clear as you consider the very simple circuit of two parallel resistors hooked up to a battery. Both resistors are hooked up independently of one another to the battery and therefore should get the voltage as the battery.

4

4

Taking this concept and the fact that resistance is inversely proportional to current, we find that the resistance is proportional to the ratio of voltage drop (DV) and current (I). This is called Ohm's law. It also shows that voltage and current are proportional, meaning more voltage willl result in more current. This makes sense if we consider voltage to be the reason or the push of the current.

Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Donec molestie. Sed aliquam sem ut arcu. Phasellus sollicitudin. Vestibulum condimentum facilisis nulla. In hac habitasse platea dictumst. Nulla nonummy. Cras quis libero. Cras venenatis. Aliquam posuere lobortis pede. Nullam fringilla urna id leo. Praesent aliquet pretium erat. Praesent non odio. Pellentesque a magna a mauris vulputate lacinia. Aenean viverra. Class aptent taciti sociosqu ad litora torquent per conu

 

Website maintained by Volker Krasemann.