Motion in Electric and Magnetic Fields – Rankers Physics

Force Acting on Moving Charges: Practice Problem & Solution

A uniform electric field and a 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
Speed will decrease
Speed will increase
Will turn towards right of direction of motion
Will turn towards left of direction of motion

Solution Explained:

To solve this problem, we apply the core principles of Force Acting on Moving Charges. Understanding the underlying formula is key to arriving at the correct answer below:

The magnetic force on the electron is \(F_m = q(\vec{v} \times \vec{B}) = 0\) since they are parallel. The electric force is \(F_e = -eE\), which acts opposite to its velocity, causing the electron to decelerate and decrease its speed.

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