How exactly do pins work?

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1

I am trying to understand how hooking an analog pin up to a circuit affects the circuit. I have the simple circuit shown in the picture and I have the analog pin taking a reading from in between two resistors. What is I2 going to be and why? Is I2 just going to be very small or nothing at all. Is the smallness of it dependent on the sizes of the resistors?

Edit: Changed the question to ask about I2 which is what I meant to ask.

circuit.png

2

BobTheAverage:
I am trying to understand how hooking an analog pin up to a circuit affects the circuit. I have the simple circuit shown in the picture and I have the analog pin taking a reading from in between two resistors. What is I3 going to be and why? Is I3 just going to be very small or nothing at all.

Did you mean I2 (the current going to the analog pin)?

Analog pins have a resistance of about 100 million Ohms. The effect on the rest of the circuit (ie. I2) will be small enough to ignore.

BobTheAverage:
Is the smallness of it dependent on the sizes of the resistors?

Only if the other resistors are also in the hundreds of millions of Ohms range.

3

I1= I3 = 5V/(R1 + R2)

I2 will be next to nothing, analog input resistance is very high.
R1+ R2 should be in the 10K range total.

4

Thanks guys. This is exactly the clarity I was hoping for.