Question 933 of 949
A proton is moving with a velocity of \( 2 \times 10^6 \, \text{m/s} \) perpendicular to a uniform magnetic field of strength \( 0.5 \, \text{T} \). What is the magnitude of the magnetic force acting on the proton? (Charge of proton \( q = 1.6 \times 10^{-19} \, \text{C} \))
- \( 1.6 \times 10^{-13} \, \text{N} \)
- \( 1.6 \times 10^{-14} \, \text{N} \)
Correct Answer:
B
Explanation
To find the magnitude of the magnetic force acting on a proton moving in a magnetic field, we can use the formula for the magnetic force on a charged particle:
\[
F = qvB \sin(\theta)
\]
Where:
- \( F \) is the magnetic force,
- \( q \) is the charge of the particle,
- \( v \) is the velocity of the particle,
- \( B \) is the magnetic field strength,
- \( \theta \) is the angle between the velocity vector and the magnetic field vector.
### Step-by-Step Calculation
1. **Identify the Given Values**:
- Charge of the proton, \( q = 1.6 \times 10^{-19} \, \text{C} \)
- Velocity of the proton, \( v = 2 \times 10^6 \, \text{m/s} \)
- Magnetic field strength, \( B = 0.5 \, \text{T} \)
- Since the proton is moving perpendicular to the magnetic field, the angle \( \theta = 90^\circ \).
2. **Calculate \( \sin(\theta) \)**:
- For \( \theta = 90^\circ \), \( \sin(90^\circ) = 1 \).
3. **Substitute the Values into the Formula**:
\[
F = (1.6 \times 10^{-19} \, \text{C}) \times (2 \times 10^6 \, \text{m/s}) \times (0.5 \, \text{T}) \times 1
\]
4. **Perform the Multiplication**:
- First, calculate \( 1.6 \times 10^{-19} \times 2 \times 10^6 \):
\[
1.6 \times 2 = 3.2
\]
\[
10^{-19} \times 10^6 = 10^{-13}
\]
Thus, \( 1.6 \times 10^{-19} \times 2 \times 10^6 = 3.2 \times 10^{-13} \, \text{C m/s} \).
- Now multiply by \( 0.5 \):
\[
F = 3.2 \times 10^{-13} \times 0.5 = 1.6 \times 10^{-13} \, \text{N}
\]
### Conclusion
The magnitude of the magnetic force acting on the proton is:
\[
\boxed{1.6 \times 10^{-13} \, \text{N}}
\]
### Explanation of Other Options
- **Option A**: [blank] - No value provided, so cannot be considered.
- **Option C**: [blank] - No value provided, so cannot be considered.
- **Option D**: \( 1.6 \times 10^{-14} \, \text{N} \) - This value is incorrect because it is an order of magnitude lower than the calculated force. The calculations clearly show that the force is \( 1.6 \times 10^{-13} \, \text{N} \), which is ten times greater than this option.
### Revision Summary
- The magnetic force on a charged particle is calculated using \( F = qvB \sin(\theta) \).
- For a proton moving perpendicular to the magnetic field, \( \sin(90^\circ) = 1 \).
- Substitute the values of charge, velocity, and magnetic field strength to find the force.
- The correct answer is \( 1.6 \times 10^{-13} \, \text{N} \).