Assertion: When a magnetic dipole is placed in a non-uniform magnetic field, only a torque acts on the dipole.
Reason: Force would also acts on dipole if magnetic field were uniform.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is the correct explanation of assertion.
C. If assertion is true but reason is false
D. If both assertion and reason are false.

Explanation

To analyze the given assertion and reason, we will break down the concepts involved step by step.

### Step 1: Understanding Magnetic Dipoles
A magnetic dipole consists of two equal and opposite magnetic poles (north and south) separated by a small distance. The magnetic moment (μ) of the dipole is a vector quantity that represents the strength and direction of the dipole.

**Hint:** Recall the definition of a magnetic dipole and its properties.

### Step 2: Magnetic Dipole in a Non-Uniform Magnetic Field
When a magnetic dipole is placed in a non-uniform magnetic field, the magnetic field strength varies from one point to another. This means that the forces acting on the north and south poles of the dipole will be different due to the variation in the magnetic field.

**Hint:** Consider how the magnetic field strength affects the forces on the poles of the dipole.

### Step 3: Analyzing Forces in a Non-Uniform Magnetic Field
In a non-uniform magnetic field, the force (F) on each pole can be expressed as:
- \( F_N = \mu B_N \) (force on the north pole)
- \( F_S = \mu B_S \) (force on the south pole)

Since \( B_N \) and \( B_S \) are not equal, the net force acting on the dipole is not zero. Additionally, the difference in forces creates a torque (τ) that tends to align the dipole with the field.

**Hint:** Think about how the difference in magnetic field strength at the poles leads to a net force and torque.

### Step 4: Magnetic Dipole in a Uniform Magnetic Field
In a uniform magnetic field, the magnetic field strength is constant throughout the region. Therefore, the forces acting on the north and south poles of the dipole are equal in magnitude but opposite in direction.

**Hint:** Visualize how a uniform magnetic field affects the forces on each pole of the dipole.

### Step 5: Analyzing Forces in a Uniform Magnetic Field
In this case, since the forces are equal and opposite, the net force on the dipole is zero. However, the dipole will still experience a torque that tends to align it with the direction of the magnetic field.

**Hint:** Remember that while the net force is zero, the torque can still exist in a uniform magnetic field.

### Conclusion
- **Assertion:** The statement that only a torque acts on the dipole in a non-uniform magnetic field is **false** because there is also a net force acting on it.
- **Reason:** The statement that a force would act on the dipole if the magnetic field were uniform is also **false** because the net force in a uniform magnetic field is zero.

Thus, both the assertion and reason are false.

**Final Answer:** Option B: Both assertion and reason are false.