Question

A uniform electric field and uniform magnetic field are acting along the same direction in a certain region. If an electron is projected in the region such that its velocity is pointed along the direction of fields, then the electron

• A. will turn towards the right direction of motion.
• B. speed will decrease.
• C. speed will increase.
• D. will turn towards the left direction of motion.

Hint:

When an electron moves in a region with both electric and magnetic fields in the same direction, the magnetic force opposes its motion, causing a decrease in speed.

Answer 1

The Correct Option is B

Step 1: Understand the motion of an electron in electric and magnetic fields.
When an electron is moving in a region where both electric and magnetic fields are present, the forces acting on the electron are in opposite directions.
Step 2: Conclusion.
Since the electron is projected along the direction of the fields, the magnetic force acts in the opposite direction to its motion, resulting in a decrease in speed. Final Answer: \[ \boxed{\text{Speed will decrease.}} \]