The correct option is Ω.
Explanation
Electrical resistance is a measure of the opposition to the flow of electric current in a circuit. The International System of Units (SI) defines the unit of electrical resistance as the Ohm.
Analysis of Options:
- Ω is Correct: The symbol Ω (Greek capital letter Omega) represents the Ohm, which is the SI unit of electrical resistance. One Ohm is defined as the resistance between two points of a conductor when a constant potential difference of one volt, applied between these points, produces in this conductor a current of one ampere ($1 \Omega = 1 V/A$).
- α is Incorrect: The symbol α (Alpha) is commonly used in physics to denote angular acceleration, the temperature coefficient of resistance, or alpha particles.
- β is Incorrect: The symbol β (Beta) is typically used to represent beta particles in nuclear physics or the current gain factor in transistors.
- γ is Incorrect: The symbol γ (Gamma) is generally used to denote gamma rays, the adiabatic index (ratio of specific heats), or surface tension.
Key Takeaway:
The SI unit of electrical resistance is the Ohm, symbolically represented by the Greek letter Ω.