Define SI unit of current in terms of the force between two parallel current carrying conductors.
(b) Two long straight parallel conductors carrying steady currents `I_(a)andI_(b)` along the same direction are separated by a distance d. How does one explain the force of attraction between them ? If a third conductor carrying a current `I_(c)` in the opposite direction is placed just in the middle of these conductors , find the resultant force acting on the third conductor.

Explanation

### Step-by-Step Solution

**(a) Definition of SI Unit of Current:**

1. **Understanding the Concept**: The SI unit of electric current is defined based on the force between two parallel conductors carrying electric currents.

2. **Definition**: The SI unit of current, known as the ampere (A), is defined as the constant current that, when maintained in two straight parallel conductors of infinite length, with negligible circular cross-section, and placed 1 meter apart in vacuum, produces a force of \(2 \times 10^{-7}\) newton per meter of length between them.

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