What is the SI unit of electrical resistance?

**The reasoning** Electrical resistance measures how much a material *opposes* the flow of electric current. Think of it like friction for electricity. The SI unit for resistance is the **Ohm (Ω)**, named after German physicist Georg Ohm. Here's how it connects: Ohm's Law states that **V = IR** (Voltage = Current × Resistance). When we rearrange this to R = V/I, we see that resistance equals voltage divided by current. So 1 Ohm = 1 Volt / 1 Ampere. **Why the wrong options tempt you** - **Volt (A)** measures electrical *potential difference* or "push" — it's what drives current, not what resists it. - **Ampere (B)** measures the *flow* of current itself — the thing being resisted, not the resistance. - **Watt (D)** measures *power* (energy per second) — how fast energy is used. It's calculated as P = VI. All four are electrical units, so they cluster together in your mind during exams. That's the trap. **Quick takeaway** **Resistance = Ohm.** Remember: "Ohm resists" — when current tries to flow, Ohms fight back. Lock that in and you'll never confuse it with Volts, Amps, or Watts again!