Question

An electron is travelling horizontally towards east. A magnetic field in vertically downward direction exerts a force on the electron along
A. East
B. West
C. North
D. South

Answer 1

The magnetic impact on moving electric charges, electric currents, and magnetic materials is described by a magnetic field, which is a vector field. In a magnetic field, a moving charge experiences a force that is perpendicular to both its own velocity and the magnetic field. The magnetic field of a permanent magnet attracts or repels other magnets, as well as ferromagnetic elements like iron.

Complete step by step solution:
One of a pair of visual mnemonics for finding out the direction of motion in an electric motor is Fleming's left-hand rule for electric motors. When current runs through a conducting wire and an external magnetic field is placed across it, the conducting wire is subjected to a force that is perpendicular to both the field and the current flow direction (i.e they are mutually perpendicular). As illustrated in the picture, a left hand may be used to depict three mutually orthogonal axes on the thumb, forefinger, and middle finger. After that, each finger is allocated to an amount (mechanical force, magnetic field and electric current).

Hold your left hand's forefinger, middle finger, and thumb at right angles to one another, according to Fleming's left hand rule. Adjust your hand so that the forefinger points in the direction of the magnetic field and the middle finger points in the direction of the current, then the direction of force acting on the conductor is determined by the thumb. Because an electron is travelling east, the current is flowing west and the magnetic field is pointing downwards. Now, with your middle finger pointed west and your forefinger pointing downward, your thumb will be pointing south. As a result, the force is moving southward.
Hence option D is correct

Note:
Some activities are used in this method of remembering which finger symbolises which quantity. To begin, position your fingers in the direction of a pretend gun, with the index finger acting as the barrel and the thumb acting as the hammer. Then perform the following steps.
Output "Fire the Field" using your index finger.
Feel the pistol recoil up through your thumb and "feel the force."
Finally, you "kill the current" by displaying your middle finger.