Question

Which set of conditions must be satisfied in the definition of the ampere?

Options

• Infinitely long, straight, parallel conductors of negligible circular cross-section, placed 1 metre apart in a vacuum

• Infinitely long, straight, perpendicular conductors placed 1 metre apart in a vacuum

• Finite-length, curved conductors of large cross-section, placed 1 metre apart in air

• Infinitely long, straight, parallel conductors placed 1 centimetre apart in a paramagnetic medium

Answer 1

The definition of the ampere specifically requires two infinitely long, straight, parallel conductors of negligible circular cross-section, separated by 1 metre in a vacuum, so that the ideal force per unit length of 2 × 10⁻⁷ N/m is obtained.