A power transmission cable made of copper consists of three segments with varying radii. Segments A and C have the same radius of 5.0 cm and are thrice that of segment B as shown below. The current passing through segment A is 1000 A. Calculate the current density J in each of these three segments.

• A. J_A = 1.3 × 10⁵ A/m², J​_B​​​ = 1.1 × 10⁶ A/m², J_C = 1.3 × 10⁵ A/m²
• B. J_A = 1.3 × 10⁵ A/m², J​_B​​​ = 1.3 × 10⁶ A/m², J_C = 3.3 × 10⁵ A/m²
• C. J_A = 1.3 × 10⁵ A/m², J​_B​​​ = 1.1 × 10⁶ A/m², J_C = 1.3 × 10⁶ A/m²
• D. J_A = 1.3 × 10⁵ A/m², J​_B​​​ = 1.3 × 10⁶ A/m², J_C = 3.3 × 10⁶ A/m²

Answer: (A)