Answer:
1) The total charge of the top plate is 0.008 C
b) The total charge of the bottom plate is -0.008 C
2) The electric field at the point exactly midway between the plates is 0
3) The electric field between plates is approximately 1.1294 × 10¹² N/C
4) The force on an electron in the middle of the two plates is approximately 1.807 × 10⁻⁷ N
Explanation:
The given parameters of the parallel plate capacitor are;
The dimensions of the plates = 4 × 2 cm
The distance between the plates = 10 cm
The surface charge density of the top plate, σ₁ = 10 C/m²
The surface charge density of the bottom plate, σ₂ = -10 C/m²
The surface area, A = 0.04 m × 0.02 m = 0.0008 m²
1) The total charge of the top plate, Q = σ₁ × A = 0.0008 m² × 10 C/m² = 0.008 C
b) The total charge of the bottom plate, Q = σ₂ × A = 0.0008 m² × -10 C/m² = -0.008 C
2) The electrical field at the point exactly midway between the plates is given as follows;
![V_{tot} = V_{q1} + V_{q2}](https://tex.z-dn.net/?f=V_%7Btot%7D%20%3D%20V_%7Bq1%7D%20%2B%20V_%7Bq2%7D)
![V_q = \dfrac{k \cdot q}{r}](https://tex.z-dn.net/?f=V_q%20%3D%20%5Cdfrac%7Bk%20%5Ccdot%20q%7D%7Br%7D)
Therefore, we have;
The distance to the midpoint between the two plates = 10 cm/2 = 5 cm = 0.05 m
![V_{tot} = \dfrac{k \cdot q}{0.05} + \dfrac{k \cdot (-q)}{0.05} = \dfrac{k \cdot q}{0.05} - \dfrac{k \cdot q}{0.05} = 0](https://tex.z-dn.net/?f=V_%7Btot%7D%20%3D%20%20%5Cdfrac%7Bk%20%5Ccdot%20q%7D%7B0.05%7D%20%2B%20%5Cdfrac%7Bk%20%5Ccdot%20%28-q%29%7D%7B0.05%7D%20%20%3D%20%5Cdfrac%7Bk%20%5Ccdot%20q%7D%7B0.05%7D%20-%20%5Cdfrac%7Bk%20%5Ccdot%20q%7D%7B0.05%7D%20%3D%200)
The electric field at the point exactly midway between the plates,
= 0
3) The electric field, 'E', between plates is given as follows;
![E =\dfrac{\sigma }{\epsilon_0 } = \dfrac{10 \ C/m^2}{8.854 \times 10^{-12} \ C^2/(N\cdot m^2)} \approx 1.1294 \times 10^{12}\ N/C](https://tex.z-dn.net/?f=E%20%3D%5Cdfrac%7B%5Csigma%20%7D%7B%5Cepsilon_0%20%7D%20%3D%20%5Cdfrac%7B10%20%5C%20C%2Fm%5E2%7D%7B8.854%20%5Ctimes%2010%5E%7B-12%7D%20%5C%20C%5E2%2F%28N%5Ccdot%20m%5E2%29%7D%20%5Capprox%201.1294%20%5Ctimes%2010%5E%7B12%7D%5C%20N%2FC)
E ≈ 1.1294 × 10¹² N/C
The electric field between plates, E ≈ 1.1294 × 10¹² N/C
4) The force on an electron in the middle of the two plates
The charge on an electron, e = -1.6 × 10⁻¹⁹ C
The force on an electron in the middle of the two plates,
= E × e
∴
= 1.1294 × 10¹² N/C × -1.6 × 10⁻¹⁹ C ≈ 1.807 × 10⁻⁷ N
The force on an electron in the middle of the two plates,
≈ 1.807 × 10⁻⁷ N