In the described right-hand rule for magnetic force, which finger indicates the velocity of the particle?

In the described right-hand rule for magnetic force, which finger indicates the velocity of the particle?

• A. Thumb
• B. Pointer finger
• C. Middle finger
• D. Pinky finger

Answer: (B)

The right-hand rule here helps you find the direction of the magnetic force on a moving charge using F = q v × B. In this version, point the index finger in the direction of the particle’s velocity. Then point the middle finger in the direction of the magnetic field. The thumb will point in the direction of the magnetic force on a positive charge (for a negative charge, the force flips). So the velocity is indicated by the index finger. The other fingers are used to establish the cross-product relationship, not to indicate velocity.

The right-hand rule here helps you find the direction of the magnetic force on a moving charge using F = q v × B. In this version, point the index finger in the direction of the particle’s velocity. Then point the middle finger in the direction of the magnetic field. The thumb will point in the direction of the magnetic force on a positive charge (for a negative charge, the force flips). So the velocity is indicated by the index finger. The other fingers are used to establish the cross-product relationship, not to indicate velocity.