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

Given:

An electron moves with constant velocity along the axis of a current-carrying solenoid.

Step 1: Recall the Magnetic Force Formula

The magnetic force (\( \vec{F}_m \)) experienced by a charged particle with charge (\( q \)) moving with velocity (\( \vec{v} \)) in a magnetic field (\( \vec{B} \)) is given by:

\[ \vec{F}_m = q (\vec{v} \times \vec{B}). \]

Step 2: Analyze the Force on the Electron

Inside a solenoid, the magnetic field (\( \vec{B} \)) is uniform and directed along the axis of the solenoid.

• The electron is moving along the axis of the solenoid, so its velocity (\( \vec{v} \)) is parallel to the magnetic field (\( \vec{B} \)).
• The cross product (\( \vec{v} \times \vec{B} \)) is zero when \( \vec{v} \) is parallel to \( \vec{B} \).

Thus, the magnetic force on the electron is:

\[ \vec{F}_m = 0. \]

Step 3: Determine the Motion of the Electron

Since the magnetic force on the electron is zero, there is no net force acting perpendicular to its motion. As a result:

• The electron will continue to move along the axis of the solenoid with constant velocity.
• It will not be accelerated, nor will it follow a curved or parabolic path.

Final Answer:

The electron will not experience a magnetic force (B), and it will continue to move along the axis of the solenoid (C).