What effect do resistors have when connected in series?

When resistors are connected in series, they combine their resistance values, resulting in an increase in the total or equivalent resistance of the circuit. This increase can lead to a reduction in the overall current flowing through the circuit, according to Ohm's Law, which states that current (I) is equal to voltage (V) divided by resistance (R). Therefore, if the total resistance increases while the applied voltage remains constant, the current must decrease.

Each resistor in a series configuration takes up a portion of the total voltage supplied to the circuit, which means that the voltage across each resistor is a fraction of the total voltage. However, the key takeaway in understanding the effect of series resistors is how they enhance the total resistance of the circuit, thereby impacting the current flow.

Given these principles, the correct choice emphasizes that the presence of multiple resistors in series results in an overall reduction of current within the circuit due to the increase in total resistance. This relationship is fundamental to circuit analysis and is a key concept in electronics.