Three identical bulbs are joined one after another to one cell. A fourth bulb is added in the same line. What happens?

1. Bulbs joined one after another form a series circuit with one pathway only. 2. Each bulb acts as a resistor in that single pathway. 3. Adding a fourth bulb raises the total resistance of the circuit. 4. A higher resistance with the same cell means a smaller current. 5. A smaller current makes every bulb glow less brightly than before. 6. They do not switch off, because a small current still flows through them all. _Source: Siyavula Natural Sciences Grade 8 (CC BY 4.0), What happens when we add more resistors in series?_