If `phi` = 90, then the magnitude of magnetic flux is?

Options

A. `F _(m) = qvb`
B. 1
C. Zero
D. `10 ^(-8)`

Explanation

To find the magnitude of magnetic flux when the angle \( \phi \) is 90 degrees, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Formula for Magnetic Flux**:
The magnetic flux \( \Phi \) is given by the formula:
\[ \Phi = B \cdot A \cdot \cos(\phi) \]
where:
- \( \Phi \) is the magnetic flux,
- \( B \) is the magnetic field strength,
- \( A \) is the area through which the magnetic field lines pass,
- \( \phi \) is the angle between the magnetic field lines and the normal (perpendicular) to the surface.

2. **Substitute the Given Value**:
In this case, we are given that \( \phi = 90^\circ \). We can substitute this value into the formula:
\[ \Phi = B \cdot A \cdot \cos(90^\circ) \]

3. **Calculate \( \cos(90^\circ) \)**:
The cosine of 90 degrees is:
\[ \cos(90^\circ) = 0 \]

4. **Simplify the Equation**:
Now substituting \( \cos(90^\circ) \) into the equation:
\[ \Phi = B \cdot A \cdot 0 \]

5. **Final Result**:
Since anything multiplied by 0 is 0, we find:
\[ \Phi = 0 \]

Thus, the magnitude of the magnetic flux when \( \phi = 90^\circ \) is **0**.

### Conclusion:
The correct answer is option 3: **0**.