What does a resistor do in a circuit?

If there is but one resistor in the circuit, it will limit the current flow according to E = I*R

If there are two resistors in series in the circuit, they will affect a voltage divider.

Though you haven't asked for it, the voltage drop across the 3 ohm resistor is E = I*R

I = 5 amps

R = 3 ohms

E = 5 * 3 = 15 Volts

And through the 2 ohm resistor, you get

I = 5 amps

R = 2 ohms

E = 2*5

E = 10 volts.

So the total is 10 v + 15 v = 25 volts

Each resistor then has a reading in voltage across it. That is called a voltage divider.

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One "resistor" like a light bulb is made to give light and also to limit the current.