Our Objective

To demonstrate repulsion/attraction between two conductors carrying current in opposite/same direction.

The Theory 

Currents in same direction 

Consider two conductors (a and b) are carrying current I_a and I_b. Conductors are placed at a distance of d. 

Conductor b experiences a force due to magnetic field of current carrying conductor a.  

Magnetic field due to current in conductor a.   

 µ₀ = 4π × 10^-7 H/m 

We get direction of magnetic field due to current Ia acting on conductor b is downward when we apply right hand thumb rule. 

Force on b due to magnetic field B_a.

• Applying right hand rule for cross products for L and B_a direction of F_bais towards conductor a. 
• Force on a due to magnetic field of current carrying conductor b (F_ab)= - F_ba
• F_ba is towards conductor b.  
• F_ba and F_ab attractive forces. 

Currents in opposite direction 

Consider two conductors (a and b) are carrying current I_a and I_b. Conductors are placed at a distance of d. I_a and I_b are in opposite directions. 

• Force on conductor b due to magnetic field of current in conductor a is in direction away from conductor a. 
• Force on conductor a due to magnetic field of current in conductor b is in direction away from conductor b.  
• Here F_ab and F_ba are repulsive forces.  

Right hand rule for cross products 

a and b are two vectors. When we sweep our fingers from the direction of a to direction of b, direction of thumb gives direction of cross product (a x b). 

Right hand thumb rule  

Curl the palm of your right hand around the circular wire with the fingers pointing in the direction of the current. The right-hand thumb gives the direction of the magnetic field. 

Learning Outcomes 

• Students can understand the concept of parallel and antiparallel currents. 
• Students can be able to find the direction of force due to magnetic field and direction of magnetic field.