cathode ray tubes

Describe how the velocity of the electron changes as it passes through the deflection plates. Your answer should firstly discuss the horizontal and vertical components of the velocity, before describing the total velocity.

The electric field creates a vertical force on the electron. This accelerates the electron in the vertical, but not horizontal frame.

The electrons horizontal velocity is unchanged, while the vertical velocity increases. The total velocity of the electron will increase.

Discuss how the electrostatic potential energy of the electrons changes as they travel through the deflection plates, and relate this to the total velocity of the electron.

Since the velocity of the electron increases slightly, the electron has more kinetic energy when it exits the field. This increase in kinetic energy has come from the conversion of electrostatic potential energy as the electron gets closer to the positive plate.

State what happens to the electrostatic force on the electron as it moves towards one of the deflection plates. Justify your answer.

The electrostatic (or electric) force does not change size or direction as the electron gets closer to the positive plate. This is because the electric field is uniform (constant) between the parallel plates as long as the voltage (150 V) or the distance (5 mm) is not changed.

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