IB Physics SL D.2.9 Parallel-plate field

Practise linking potential difference, plate separation and electric field strength in uniform parallel-plate fields, including forces, energy changes and equilibrium.

Exam points

calculate E between plates from E = V/d, or from the gradient of a potential-distance graph
apply qE = mg for a charged particle at rest between plates to determine q, V or the plate spacing
link particle motion to field direction and predict kinetic energy change from the potential difference crossed

[Maximum number: 1]

Two oppositely charged parallel plates are a distance 8.0 cm apart. The potential difference between the plates is 120 V . An alpha particle is placed on the positively charged plate and released from rest. Gravity is ignored.

Figure for Question D.2.9—Parallel-plate field question 1 — IB Physics SL

Calculate the electric field between the plates.

$E=\ll \frac{120}{8.0 \times 10^{-2}}=>1.5 \times 10^{3} N C^{-1} \boldsymbol{O} \boldsymbol{R} \mathrm{Vm}^{-1}$

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D.2.9—Parallel-plate field question 1