On a desktop computer case, leaving expansion card slot covers missing can primarily lead to which type of problem?

Introduction / Context:
Desktop computer cases are designed with metal covers for unused expansion slots at the back of the case. These slot covers may seem unimportant, but they play a role in both safety and signal integrity. When covers are missing, the case is no longer fully enclosed. This question asks what type of problem is most directly associated with missing slot covers on a computer case, focusing on the effect on electromagnetic behaviour and system protection.

Given Data / Assumptions:
- We are discussing the rear panel of a desktop computer case where expansion cards are mounted.
- Some slots are unused and normally have metal covers installed.
- Those covers have been left off or removed, leaving openings in the metal enclosure.
- We want the primary technical problem that this situation can cause.

Concept / Approach:
A metallic computer case acts as a partial shield against electromagnetic interference, both preventing internal signals from radiating outward and reducing the influence of external electromagnetic fields on internal components. This is often called a Faraday cage effect. When slot covers are missing, the case has larger openings through which electromagnetic radiation can escape or enter. This can increase electromagnetic interference (EMI), which may affect sensitive components or cause problems with nearby equipment. While missing slot covers can also allow dust and warm air to move differently, the specific technical risk most often mentioned in certification exams is increased EMI. Power surges on the mains supply and incomplete electrostatic discharge paths are not primarily caused by missing slot covers, and monitor overheating is unrelated.

Step-by-Step Solution:
Step 1: Recall that a metal system unit case functions as an electromagnetic shield, helping to contain internal signals and block external interference. Step 2: Understand that expansion slot covers are part of this shielding structure. When they are installed, the back panel is mostly continuous metal. Step 3: If covers are missing, large gaps open in the rear of the case, reducing the effectiveness of the shielding. Step 4: Reduced shielding allows more electromagnetic radiation to leak out and more external interference to enter, which increases the risk of EMI affecting the system or nearby devices. Step 5: Consider the other options. Power surges are related to voltage spikes in the mains supply, not to holes in the computer case. ESD paths depend on grounding and handling procedures, not slot covers. Monitor temperature is unrelated to openings in the system unit. Step 6: Conclude that the primary problem associated with missing slot covers is increased electromagnetic interference.

Verification / Alternative check:
Hardware maintenance training materials often mention that technicians should replace slot covers after removing expansion cards. They note that missing covers can compromise electromagnetic compatibility by allowing signals to escape the enclosure and possibly interfere with nearby equipment. Regulatory standards on electromagnetic emissions assume that equipment is operated with all covers in place. These references make much less mention of power surges or monitor overheating related to missing covers, which supports EMI as the main concern highlighted by the question.

Why Other Options Are Wrong:
Power surges on the mains electrical supply: These originate from the power grid or power supply faults and are not caused by mechanical openings in the case.
An incomplete path for electrostatic discharge (ESD): ESD protection depends on grounding, handling procedures, and circuit design, not on whether slot covers are installed.
Overheating of the monitor only: The monitor is a separate device and its temperature is not meaningfully affected by missing slot covers on the system unit.

Common Pitfalls:
Some learners may associate any opening in the case with overheating because openings can affect airflow. While airflow can change, modern cases typically have ventilation paths and fans designed for cooling, and missing a few slot covers does not always cause significant thermal issues. The exams that ask this question focus instead on electromagnetic compliance and shielding. To avoid confusion, remember that the metal enclosure is primarily an EMI shield, and missing pieces reduce its ability to block radiation, making EMI the key issue.

Final Answer:
Missing slot covers can primarily cause Increased electromagnetic interference (EMI) inside and outside the case.