In a cyclotron, a charged particle

Options

A. undergoes acceleration all the time.
B. speeds up between the dees because of the magnetic field.
C. speeds up in a dee.
D. slows down within a dee and speeds up between dees.

Answer

### Step-by-Step Solution:

1. **Understanding the Cyclotron**: A cyclotron is a type of particle accelerator that uses electric fields to accelerate charged particles and magnetic fields to keep them in circular motion. The device consists of two D-shaped electrodes (called D's) placed in a magnetic field.

2. **Acceleration of Charged Particles**: When a charged particle enters the cyclotron, it is subjected to an electric field present in the gap between the D's. This electric field accelerates the particle, increasing its kinetic energy.

3. **Motion Between the D's**: As the particle moves between the D's, it is accelerated by the electric field. This acceleration occurs because the electric field is directed in such a way that it pushes the particle forward.

4. **Uniform Circular Motion**: Once the particle enters the D's, it experiences a magnetic field that causes it to move in a circular path. The magnetic field provides the necessary centripetal force to keep the particle in this circular motion.

5. **Change of Electric Field**: As the particle exits one D and enters the gap again, the polarity of the electric field changes, allowing the particle to be accelerated again. This cycle continues, with the particle gaining energy each time it passes through the gap.

6. **Conclusion**: The charged particle undergoes continuous acceleration as it moves through the cyclotron. It speeds up in the gaps between the D's due to the electric field and maintains uniform circular motion due to the magnetic field.

### Final Answer:
The charged particle in a cyclotron undergoes acceleration all the time.