Concepts Of Physics MCQ Edition [Volume 2]PhysicsElectric Field and Potential
As one travels along the x -axis from x = -1 cm to x = +1 cm , the electric potential decreases uniformly from 120 V to 80 V . Which of the following is true regarding the electric field at the origin?
Options
- AIt must be equal to 20 V cm ⁻¹
- BIt may be less than 20 V cm ⁻¹
- CIt may be equal to 20 V cm ⁻¹
- DIt may be greater than 20 V cm ⁻¹
Correct answer
D. It may be greater than 20 V cm ⁻¹
Step-by-step solution
The x -component of the electric field is given by E_ x = - V x . Since the potential decreases uniformly along the x -axis, we have E_ x = - V x = - 80 - 120 1 - (-1) = 20 V cm ⁻¹ . The total electric field is E = E_ x i + E_ y j + E_ z k . The magnitude of the electric field is E = E_ x ^2 + E_ y ^2 + E_ z ^2 = 20^2 + E_ y ^2 + E_ z ^2 . Since the variation of potential along the y and z axes is not given, E_ y and E_ z are unknown and can be zero or non-zero. Therefore, E 20 V cm ⁻¹ . Thus, the magnitude of the