Having trouble understanding the concept of current and Ohms law Circuit in series: $10\,\text{V}$ power supply, 2 resistors connected. Each resistor is $10\,\Omega$, total of $20\,\Omega$ resistance.
If I put an ammeter at the end of the circuit, will the current be calculated using 20 Ohms or 10? Electrons flow through the first 10 Ohm resistor and are slowed down, yes? Then they flow through the second 10 Ohm resistor. They have passed through a total of 20 Ohms BUT at 10 Ohms per resistor. 
Will the current be the same as if it had passed through 1 20 Ohm resistor? That violates everything I understand.
 A: The current $I$ has a value in one point of the circuit, in contrast to the
voltage $U$ which is always measured between 2 points.
The definition of $I$ is the amount of charge $\Delta q$ that passes through a particular point in the circuit in the time $\Delta t$ (it's a quantity mathematically similar to the simple velocity in kinematics). So when you measure the current in one particular place of the circuit, you measure how much charge is passing through that point, divided by time.
So what do you think is the difference in the measured current $I$, if in between the power supply $U$ and the measuring point you have:


*

*one resistor with $R = 20$ $\Omega$

*2 resistors, each with $R = 10$ $\Omega$

*4 resistors, each with $R = 5$ $\Omega$
etc.?

A: If you rearrange Ohm's Law equation, you get $I=\frac {V}{R}$. When you have 2 equal resistors in series, the voltage drop across each resistor is $\frac {1}{2}$ the total voltage. Now calculate the current through both resistors, through one resistor and the equivalent resistor (20 ohms).
