Question 2 of 22intermediate💡 UnderstandMCQ1 mark

Which of the following property of a proton can change while it moves freely in a magnetic field? (There may be more than one correct answer.)

Exercise: QUESTIONS | Q: 1 | (Chapter: Page 9)
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Explanation

The textbook context states that the direction of force acting on a charged particle (like an electron or proton) in a magnetic field is perpendicular to both the magnetic field and the direction of motion, as given by Fleming's left hand rule. When a proton moves freely in a magnetic field, the magnetic force acts perpendicular to its velocity. This perpendicular force does no work on the proton, so its kinetic energy and thus speed remain constant. However, since the force changes the direction of motion, the velocity (which is a vector quantity with both magnitude and direction) changes. As momentum equals mass times velocity (p = mv), and velocity changes while mass remains constant, momentum also changes. Mass is an intrinsic property that cannot change in this scenario.

Solution Steps

  1. Step 1: Identify that magnetic force on a moving charged particle is perpendicular to its velocity (from Fleming's left hand rule mentioned in context)

  2. Step 2: Since force is perpendicular to motion, no work is done, so speed remains constant

  3. Step 3: Velocity changes because direction changes (velocity is a vector)

  4. Step 4: Momentum changes because momentum = mass × velocity, and velocity changes

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