An 800-KHz Radio Signal Is Detected at a Point 8

question 14

Multiple Choice

An 800-kHz radio signal is detected at a point 8.5 km distant from a transmitter tower.The electric field amplitude of the signal at that point is 0.90 V/m.Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed.What is the average electromagnetic energy density at that point? (c = 3.0 × 10⁸ m/s,μ₀ = 4π × 10^-7 T ∙ m/A,ε₀ = 8.85 × 10^-12 C²/N ∙ m²)

• A)3.6 pJ/m³
• B)5.1 pJ/m³
• C)7.2 pJ/m³
• D)10 pJ/m³
• E)14 pJ/m³

---

Definitions:

Variable Manufacturing Overhead

The portion of manufacturing overhead costs that varies with production volume.

Variable Overhead Efficiency Variance

Variable overhead efficiency variance is the difference between the actual and budgeted variable overhead cost based on the efficient utilization of resources.

Direct Labor-hours

The amount of labor hours that can be directly attributed to the production process, serving as a basis for allocating manufacturing overhead costs in some costing systems.

Variable Manufacturing Overhead Standards

Pre-set rates used to allocate variable overhead costs to individual units of production based on expected usage criteria, such as labor hours.