Two linear parallel conductors carrying currents in the same direction attract each other and two linear parallel conductors carrying currents in opposite direction repel each other. The force acting per unit length due to currents `I_1` and `I_2` in two linear parallel conductors held distance r apart in vacuum in SI unit is `F=(mu_0)/(4pi)(2I_1I_2)/(r)`
Read the above passage and answer the following questions:
(i) What is the basic reason for the force between two linear parallel conductors carrying currents?
(ii) Two straight wires A and B of lengths `2cm` and `20cm`, carrying currents `2*0A` and `5*0A` respectively in opposite directions are lying parallel to each other `4*0cm` apart. The wire A is held near the middle of wire B. What is the force on `20cm` long wire B?
(iii) What does this study imply in day to day life?

Explanation

(i) The force is due to interaction between magnetic fields due to currents in two linear parallel conductors.
(ii) Here, `l_1=2cm=2xx10^-2m`, `l_2=20xx10^-2m`, `I_1=2*0A`, `I_2=5*0A`, `r=4xx10^-2m`.
Since, action and reaction are equal and opposite so the magnitude of repulsive force on `20cm` long wire
= the magnitude of repulsive force on `2cm` long wire `=(mu_0)/(4pi)(2I_1I_2)/(r)l_1=10^-7xx(2xx2xx5xx(2xx10^-2))/(4xx10^-2)`
`=10^-6N`
(iii) This study shows that when current through two parallel conductors flow in the same direction, they attract each other and vice versa. It implies that when the thoughts and actions of two business partners are aligned in the same direction, their behaviour is cohesive and they succeed. If their thoughts and actions are opposing, the partnership is likely to collapse. The same thing is true for husband and wife. For a successful family life, coherence of thoughts and actions is a must.