question_answer

In the electric field shown in Fig. the electric field lines on the left have twice the separation as that between those on the right. If the magnitude of the field at point A is\[\mathbf{40N}{{\mathbf{C}}^{\mathbf{-1}}}\], calculate the force experienced by a proton placed at point A. Also find the magnitude of electric field at point B.

Answer:

                Force on proton at point A, \[\mathbf{F=e}{{\mathbf{E}}_{\mathbf{A}}}\mathbf{=1}\mathbf{.6\times 1}{{\mathbf{0}}^{\mathbf{-19}}}\mathbf{\times 40=6}\mathbf{.4\times 1}{{\mathbf{0}}^{\mathbf{-18}}}\mathbf{N}\mathbf{.}\] As the separation between the lines of force at point B is twice of that at point A, so \[{{E}_{B}}=\frac{1}{2}{{E}_{A}}=\frac{1}{2}\times 40=20N{{C}^{-1}}\].