Two point charges qA = 3μC and qB = -3μC are located 20 cm apart in vacuum. (a) What is the electric field at the midpoint O of the line AB joining the two charges? (b) If a negative test charge of magnitude 1.5 10 power -9 C is placed at this point, what is the force experienced by the test charge? | question and answer !

Question :-

Two point charges qA = 3μC and qB = -3μC are located 20 cm apart in vacuum.

(a) What is the electric field at the midpoint O of the line AB joining the two charges?

(b) If a negative test charge of magnitude 1.5 10 power -9 C is placed at this point, what is the force experienced by the test charge?

Answer :-

(a) The situation is represented in the given figure. O is the mid-point of line AB.



Distance between the two charges, AB = 20 cm

 :. AO = OB = 10 cm

Net electric field at point O = E

Electric field at point O caused by +3μC charge,



Where,

E0 = Permittivity of free space



Magnitude of electric field at point O caused by -3μC charge,

The force is directed along line OA. This is because the negative test charge is repelled by the charge placed at point B but attracted towards point A. Therefore, the force experienced by the test charge is -8.1 x 10power -3 N along OA.