*Question E5C07:
Where is the impedance of a pure resistance plotted on rectangular coordinates?*  

*Correct Answer is  D: On the horizontal axis*  

### AI Response: (may contain errors)  

In rectangular coordinates, impedance is represented as a complex number, $Z = R + jX$, where:

- $R$ is the resistance (real part)
- $X$ is the reactance (imaginary part)
- $j$ is the imaginary unit

For a pure resistance, the reactance $X$ is zero, so the impedance simplifies to $Z = R + j0$. This means the impedance is purely real and has no imaginary component.

### Explanation:

1. **Correct Answer: On the horizontal axis**
   - In rectangular coordinates, the horizontal axis represents the real part of the impedance, which is the resistance $R$. Since a pure resistance has no reactance, it is plotted entirely on the horizontal axis.

2. **Why the other choices are incorrect:**
   - **A: On the vertical axis**
     - The vertical axis represents the imaginary part (reactance $X$). A pure resistance has no reactance, so it cannot be plotted on the vertical axis.
   - **B: On a line through the origin, slanted at 45 degrees**
     - A line at 45 degrees would imply equal real and imaginary components (i.e., $R = X$), which is not the case for a pure resistance.
   - **C: On a horizontal line, offset vertically above the horizontal axis**
     - This would imply a non-zero imaginary component (reactance), which is not present in a pure resistance.

### Summary:

For a pure resistance, the impedance is plotted on the horizontal axis in rectangular coordinates because it has no imaginary component. This is why the correct answer is "On the horizontal axis."