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WAEC Physics 2023 Paper

Question : 1

Total: 50

The electric field in the region outside the parallel plate is zero, except for the edge effects
The magnitude of the electric field strength at any point between the plates, except near the edges, depends on the magnitude of the charge on each plate.
The magnitude of the electric field strength at any point between the plates is directly proportional to the magnitude of the charge on each plate.
The electric field is uniform everywhere in the space between the parallel plates

Solution:

Concept:

The electric field in the central region between large parallel plates depends on surface charge density,

\sigma = Q/A

, and is uniform away from the edges.

Explanation:

For two large, oppositely charged parallel plates,

E = \frac{\sigma}{\varepsilon_0} = \frac{Q}{A \varepsilon_0}.

Here,

Q

is the charge on either plate and

A

is the plate area.

So the field is controlled by charge per unit area,

\sigma

, not by the total charge

Q

alone.

If the area is fixed, increasing

Q

increases

\sigma

and therefore increases

E

But if the area also changes,

E

is not determined by

Q

alone.

Thus, saying

E

is directly proportional to the charge on each plate, without mentioning the area, is not a correct general statement.

Answer:

The incorrect statement is Option C.

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