Question

An electron is allowed to move with constant velocity along the axis of current carrying straight solenoid.
A. The electron will experience magnetic force along the axis of the solenoid. 
B. The electron will not experience magnetic force. 
C. The electron will continue to move along the axis of the solenoid. 
D. The electron will be accelerated along the axis of the solenoid. 
E. The electron will follow parabolic path-inside the solenoid. 
Choose the correct answer from the options given below :

• A. A and D only
• B. B, C and D only
• C. B and C only
• D. B and E only

Answer 1

The Correct Option is C

The problem discusses an electron moving along the axis of a current-carrying straight solenoid. We need to determine the behavior of the electron under the influence of the magnetic field generated by the solenoid. 

1. First, understand the magnetic field inside a solenoid. The magnetic field inside an ideal solenoid with current is uniform and directed along the axis of the solenoid. Outside the solenoid, the field is nearly zero.
2. The magnetic force experienced by a charged particle moving in a magnetic field is given by the Lorentz force equation: \(\mathbf{F} = q(\mathbf{v} \times \mathbf{B})\), where:
   • \(q\) is the charge of the particle (negative for electrons).
   • \(\mathbf{v}\) is the velocity of the particle.
   • \(\mathbf{B}\) is the magnetic field.
   • \theta between the velocity vector \(\mathbf{v}\) and the magnetic field \(\mathbf{B}\) is 0 degrees.
   • The cross product \(\mathbf{v} \times \mathbf{B} = \|\mathbf{v}\| \|\mathbf{B}\| \sin(\theta)\).
   • Since \(\theta = 0\), \(\sin(0) = 0\), and thus \(\mathbf{v} \times \mathbf{B} = 0\).
   • Therefore, the magnetic force experienced by the electron is zero.
3. Conclusions based on analysis:
   • The electron will not experience any magnetic force (Option B).
   • As there is no force to change its velocity, the electron will continue to move along the axis of the solenoid with constant velocity (Option C).

Based on the above understanding, the correct answer is "B and C only".