Question

The magnetic force acting on a moving charge is given by the product of three quantities, namely

• A. charge, speed, electromotive force
• B. charge, magnetic flux, magnetic flux density
• C. charge, speed, magnetic flux density
• D. charge, speed, current

Answer 1

The Correct Option is C

Step 1: Recall the formula for the magnetic force on a moving charge.

The magnetic force (\( F \)) acting on a charge \( q \) moving with velocity \( v \) in a magnetic field of magnetic flux density \( B \) is given by:

\[ F = qvB \sin\theta, \]

where:

• \( q \) is the charge,
• \( v \) is the speed of the charge,
• \( B \) is the magnetic flux density (also known as the magnetic field strength), and
• \( \theta \) is the angle between the velocity vector \( v \) and the magnetic field vector \( B \).

 

Step 2: Analyze the options.

• (1) Charge, speed, electromotive force: Electromotive force (EMF) is not involved in the magnetic force on a moving charge. The force depends on the magnetic flux density, not EMF.
• (2) Charge, magnetic flux, magnetic flux density: Magnetic flux is not directly involved in the formula for magnetic force. The relevant quantity is magnetic flux density.
• (3) Charge, speed, magnetic flux density: This matches the formula \( F = qvB \sin\theta \). The force depends on the charge, speed, and magnetic flux density.
• (4) Charge, speed, current: Current is not explicitly involved in the formula for the magnetic force on a single moving charge. The force depends on the charge, speed, and magnetic flux density.

Final Answer: The correct quantities are \( \mathbf{\text{charge, speed, magnetic flux density}} \), which corresponds to option \( \mathbf{(3)} \).