How would this change affect the electric circuit? a switch is closed, so the circuit would be incomplete and broken and the lights in the circuit would not shine. a switch is closed, so the circuit would be complete and unbroken and the lights in the circuit would shine. a switch is opened, so the circuit would be incomplete and broken and the lights in the circuit would not shine. a switch is opened, so the circuit would be complete and unbroken and the lights in the circuit would shine.