Final answer:
When the currents in two parallel wires are doubled from 10A to 20A, the magnetic force of attraction between them also increases fourfold, resulting in a force of 4 mN.
Step-by-step explanation:
The question involves the concept of magnetic force between two parallel conductors from physics. According to Ampère's Force Law, the force between two parallel currents is directly proportional to the product of the currents and inversely proportional to the distance between them. When the currents in the conductors are in the same direction, the wires attract each other, whereas when the currents are in opposite directions, the wires repel each other.
In this specific scenario, we are told that two parallel wires with equal currents attract each other with a force of 1 mN when the current in each is 10A. If the currents are doubled, both currents become 20A. Using the proportionality relationship, if we double the currents in both wires, the force of attraction becomes four times stronger (since F is proportional to the product of the currents: F ≈ I1 x I2, and doubling both I1 and I2 results in a fourfold increase in F).
Therefore, if the currents are doubled in both wires from 10A to 20A, the force of attraction will become 4 mN.