Magnetic Force

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

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

where:

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

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 . 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 , which corresponds to option .

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

F = qvB sin θ, where: - q is the charge,

- v is the speed (velocity) of the charge,

- B is the magnetic flux density, - θ is the angle between the velocity vector and the magnetic field.

Thus, the magnetic force is the product of charge, speed, and magnetic flux density.