# A few circuit questions

1. Feb 24, 2005

### dayrinni

I have a couple questions about circuits.

Let's say I have a current flowing through the circuit and then it hits a resistor. The current will obviously go down while it is in the resistor but then does it stay reduced (By the strength of the resistor) for the duration of the circuit? So in theory you could put as many resistors as you needed to reduce the current to 0?

What is the relationship between the voltage on the battery and the current? A circuit with a voltage of 12 V will have that as a potential, and the current is what is actually going along the path. An example is having a highway and it's speed limit is 55 mph (It's voltage) and then the actual current is the car driving on the highway.
If that is right, I do not see why you do not measure current in terms of voltage, or a % of it along the path. Like at this point on the circuit the current is 5V (out of say 12V), not 5 A.

Thanks for any help.

2. Feb 24, 2005

### NateTG

The two basic equations for DC circuits that you should probably know:

$$I=\frac{V}{R}$$
Current (Amps) is equal to the potential difference (Volts) divided by the resistance (Ohms).
and
$$P=IV$$
The amount of power that something uses uses is equal to potential change multiplied by current.

For all but the simplest circuits, it's necessary to seperate voltage from current in order to understand what's going on.

If you think of electricity as water, then voltage is the amount of pressure that the water is under, and current is the amount that is flowing. There are situations where there is low current and high potential difference like in fountain jets, and situations where there is massive current and little potential difference - like many rivers.