Electric field, E = 2.22 V/cm
Explanation:
Given that,
The distance between 7 V equipotential and 5 V at point B is 0.9 cm. The relation between electric field and electric potential is given by :
E = 2.22 V/cm
So, the magnitude of the electric field at point B is 2.22 V/cm. Hence, this is the required solution.