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Electric Field lines and direction of force

Ela asked:

“if +Q is a positive source charge and has electric field lines coming out of it does this mean that electric field lines are in direction of force? If yes then how a source charge +Q has field lines coming out of it , attracts -e as test charge?”


Electric field (lines) are in the direction of force on a positive charge, and opposite to the direction of force on a negative charge.

In other words, in an electric field, a positive charge experiences a

Force on electron in a magnetic field

Samantha asked:

“An electron enters a magnetic field at right angles to it. The direction of force acting on the electron will be __________?”


Answer: The direction of force is given by Fleming’s Left Hand Rule.

If we stretch the thumb, forefinger and central finger of left hand in such a way that the forefinger shows the direction of magnetic field, the central finger shows the direction of movement of positive charge (or the direction of current) [here the direction must be opposite to the direction of motion of the electron since electron is negatively charged], then the direction of thumb will give the direction of force acting on the charge.

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