What is the primary effect of a cold filament in an electrical circuit?

The primary effect of a cold filament in an electrical circuit is that it has low resistance, which leads to a large in-rush current when voltage is initially applied. This phenomenon occurs because, at a lower temperature, the material of the filament—typically a metal like tungsten—exhibits significantly less resistance compared to when it is heated during operation.

When the circuit is first energized, the unheated filament allows a much larger flow of current than when it reaches its operating temperature. This large in-rush current is crucial for understanding the behavior of incandescent bulbs and similar devices, as it can be several times higher than the normal operating current, possibly causing damage if not properly managed.

The other options imply varying states of resistance and in-rush current that do not accurately reflect the behavior of a cold filament. High resistance would imply less current flow, which contradicts the effect observed when a cold filament is energized.