What is the resistance across resistor R2?

• A. 2 ohms
• B. 1 ohm
• C. 5 ohms
• D. 10 ohms

Answer: (A)

The key idea is that the resistance across a resistor is simply the resistor’s own rated value. For resistor R2, you look at the component’s label and measure across its two terminals. If R2 is a 2-ohm resistor, the resistance between its terminals is 2 ohms, which is why that option is correct. The presence of other components in the circuit doesn’t change the intrinsic resistance of R2 itself when you’re asked for the value across the resistor’s own terminals. If the question were asking for the equivalent resistance seen by the rest of the circuit looking into the points where R2 connects, we’d have to combine it with other elements, but this item asks for R2’s own resistance.