Calculate the electric field intensity between two plates of potential difference 6.5V when separated by a distance of 35cm.

Analyze the question: We need the electric field intensity (E) between two parallel plates, given the potential difference (V) and the separation (d).

Concept: For a uniform field between parallel plates:

E = V / d

Units: V/m, which is the same as N C⁻¹. The distance must be in metres.

Solution:

• V = 6.5 V
• d = 35 cm = 0.35 m

E = 6.5 / 0.35 = 18.57 V/m = 18.57 N C⁻¹

Check against the options: 18.57 N C⁻¹ matches option A.

Why the other options are wrong:

• B (53.06) does not come from V/d with the correct units.
• C (2.28) and D (0.80) do not come from any sensible use of 6.5 and 0.35. For example, 6.5 × 0.35 = 2.275, which is about 2.28, so C comes from multiplying instead of dividing.

Exam tip: Always convert cm to m before using E = V/d. If you forget and use 35 directly, you get 0.186, which is not an option. Remember it as "Field = Voltage over distance". If the answer is a large number, divide by the small distance in metres.