BTRC Assistant Director (Technical) Written Test: 2019প্রশ্ন ও সমাধান

An IC (Integrated Circuit), also called a chip or microchip, is a single semiconductor package that fabricates many transistors, resistors, diodes, and capacitors together on one small silicon die, forming a complete functional circuit.

Advantages of IC over discrete-component circuits:

Benefit	Reason
Extremely small size	Thousands of components etched onto one chip
Low weight	Massive miniaturization vs. separate discrete parts
Low cost	Mass-produced in bulk on a single wafer
High reliability	Fewer external solder joints/wires to fail
Low power consumption	Explained below
Higher operating speed	Very short signal paths between components
Easy replacement	Standardized chip packages, plug-and-play modules
Better temperature tolerance	Uniform fabrication process
Close component matching	All parts fabricated under identical conditions

Why ICs need less power:
Power consumption in a circuit is proportional to load capacitance and to the square of the operating voltage (P ∝ C·V²·f). Because every component inside an IC is microscopically small, the parasitic capacitance of each element is also extremely small, and modern ICs run at much lower voltages than discrete transistor circuits — both factors combine to cut total power sharply, which is why IC-based devices run cool and battery-friendly compared to their discrete-component equivalents.

Exam takeaway: ICs win on size, cost, reliability, and speed mainly because integration shrinks every physical dimension — and shrinking dimensions directly shrinks capacitance, which is the main driver of lower power consumption.

Two-factor authentication (2FA) requires a user to prove their identity using two different categories of evidence before granting access, so that compromising just one factor (e.g. a stolen password) is not enough to break in.

The three recognized factor categories:

1. Something you know — a password or PIN.
2. Something you have — a phone (OTP/SMS code), hardware token, or authenticator app.
3. Something you are — biometrics: fingerprint, face, retina scan.

2FA always combines exactly two of these three categories (not two instances of the same one — two passwords would not count as 2FA).

sequenceDiagram
  participant U as User
  participant Sys as Login System
  participant Ph as User's Phone
  U->>Sys: Enter username + password (factor 1)
  Sys->>Ph: Send one-time code (OTP)
  Ph-->>U: Show OTP
  U->>Sys: Enter OTP (factor 2)
  Sys-->>U: Access granted

Example: When logging into an Apple ID from a new computer, the user enters their password (something they know), then Apple sends a multi-digit verification code to their trusted iPhone (something they have); only entering both grants access.

Exam takeaway: 2FA's security strength comes from requiring two different kinds of proof — an attacker who steals a password still cannot log in without also possessing the user's physical device or biometric trait.