13. This is a schematic image of a mobile phone SIM card. What is the function of the
diagonal cut on the left side?
a. To serve as an electrical contact
b. To dissipate heat during use
c. To ensure it is inserted in the correct orientation
d. To cut costs by reducing material

The function of the diagonal cut (notch) on a mobile phone SIM card is to ensure it is inserted in the correct orientation, so the correct option is C.​​

Introduction

A SIM card may look like a small piece of plastic, but its shape is carefully engineered, especially the diagonal cut on one corner. This diagonal notch is crucial for proper orientation of the SIM card in the tray and protects both the chip and the phone from damage due to incorrect insertion.​

Correct option: C

The diagonal cut on a SIM card is a mechanical keying feature that guides users to insert the SIM in only one possible orientation. Because of this notch, the card cannot sit flat in the tray if it is upside down or reversed, so the metal contacts line up correctly with the phone’s connectors and the device can read the card safely.​

Option A: To serve as an electrical contact

The electrical contacts of a SIM card are the gold-colored metal pads in the center of the card, not the plastic edges. The diagonal cut is made in the plastic substrate, which does not carry current and plays no role in data transfer or network connectivity, so it cannot be considered an electrical contact.​

Option B: To dissipate heat during use

Heat generated during phone operation comes mainly from components such as the processor, battery, and radio modules, not from the SIM card’s plastic body. The tiny removed corner does not create a meaningful surface area or path for heat dissipation, and SIM cards are designed to tolerate normal operating temperatures without relying on that notch for cooling.​

Option C: To ensure correct orientation during insertion (Correct)

The notch is standardized so that SIM card trays and slots are designed to accept the card in only one direction, preventing wrong insertion and misalignment of contacts. This reduces user error, avoids scratching or bending the delicate contacts, and supports universal compatibility of SIM cards across different devices.​

Option D: To cut costs by reducing material

The amount of plastic removed by the diagonal cut is extremely small and has no practical impact on manufacturing cost. The shape is chosen for functionality and standardization rather than for saving material, so cost reduction is not the purpose of the notch.​