Problem

The electric flux through each surface of a cube is given below. Which surfaces of the cube does the electric field run parallel to? 

Φ1 = 100 Nm2 /C           Φ4 = 0 Nm2 /C
Φ2 = 20 Nm2 /C             Φ5 = −40 Nm2 /?
Φ3 = 0 Nm2 /C               Φ6 = −80 Nm2 /?

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