When two co-axial coils having same current in same direction are bring to each other, then the value of current in both coils:

Options

A. increase
B. decrease
C. first increases and then decrease
D. remain same

Answer

To solve the problem step by step, we will analyze the situation of two coaxial coils carrying the same current in the same direction and determine the effect on the current in both coils when they are brought close to each other.

### Step-by-Step Solution:

1. **Understanding the Setup**:
- We have two coaxial coils (let's call them Coil 1 and Coil 2) that are aligned along the same axis.
- Both coils are carrying the same current (I) in the same direction.

2. **Magnetic Field Due to Each Coil**:
- When current flows through Coil 1, it generates a magnetic field around it. The direction of this magnetic field can be determined using the right-hand rule.
- Similarly, Coil 2 also generates a magnetic field in the same direction due to the same current flowing through it.

3. **Effect of Bringing Coils Together**:
- As Coil 1 and Coil 2 are brought closer to each other, the magnetic field produced by Coil 1 will influence Coil 2 and vice versa.
- Since both coils have current flowing in the same direction, the magnetic field produced by each coil will be in the same direction as well.

4. **Induced Current According to Lenz's Law**:
- According to Lenz's Law, if the magnetic field through a coil changes, it will induce a current in the opposite direction to oppose that change.
- As the coils are brought closer, the magnetic field in each coil is increasing due to the proximity of the other coil.

5. **Determining the Induced Current**:
- The increasing magnetic field in Coil 2 (due to Coil 1) will induce a current in Coil 2 that opposes this increase. This induced current will flow in the opposite direction to the current already present in Coil 2.
- The same applies to Coil 1, where the increasing magnetic field from Coil 2 will induce a current that opposes the increase in magnetic field.

6. **Net Current in Each Coil**:
- The net current in Coil 1 will be the original current (I) minus the induced current (I_induced).
- Similarly, the net current in Coil 2 will also be the original current (I) minus the induced current (I_induced).
- Therefore, the net current in both coils will decrease as a result of the induced currents opposing the original currents.

7. **Conclusion**:
- Since the induced currents in both coils oppose the original currents, the value of the current in both coils will decrease when they are brought close to each other.

### Final Answer:
The value of the current in both coils will **decrease**.

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