Basic Physics

# Electric charges, magnetic field and magnetic forces – problems and solutions

1. If q is the positive electric charge, v is the charge motion, B is the magnetic field and F is the direction of the magnetic force, then the right figure for a charge across the magnetic field is … Solution

Meaning of the symbols x and o in the picture

Look at the pictures above. The symbol x means that the direction of the magnetic field B is perpendicularly through the monitor field (away from the reader). The symbol o means that the direction of the magnetic field B is perpendicular to the outside (close to the reader).

The direction of the electric charge (v), the direction of the magnetic field (B) and the direction of the magnetic force (F) are perpendicular to each other. The direction of electric charge movement, magnetic field, and magnetic force is determined appropriately using the right-hand rule.

Right-hand rule

Extend your right hand, straighten your thumb and tie the other four fingers together. Set the four fingers to show the direction of the magnetic field (B) and the thumb shows the direction of the charge motion (v). If the charge is positive, the right-hand palms toward the magnetic force (F). If the charge is negative, the back of the right-hand goes towards the magnetic force (F).

Apply the right-hand rule to the above drawings.

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2. A negative charge (-q) moves inside a homogeneous magnetic field B as shown in the figure. The correct image of the magnetic force experienced by the charge is … Solution

Apply the right-hand rule to the above figure.

3. A positive charge moves toward a homogeneous magnetic field perpendicularly. The correct figure of the direction of magnetic force, velocity, and the magnetic field is… Solution

Apply the right-hand rule to the above figure.