18.2.1—E = ∆V / ∆d to calculate the field strength of the uniform field between

In a uniform field, field strength magnitude is E=∆V/∆d, where ∆V is potential difference across perpendicular separation ∆d.

Use metres and volts, and remember field direction points from higher potential toward lower potential for a positive test charge.

A 600 V difference across 0.020 m gives E=3.0×10⁴ N C⁻¹.

The relation is for a uniform field; in a point-charge field strength changes with distance.