Tutorial 3: Capacitors
Course: FAD1022 Basic Physics 2
Semester: 2 2025/2026
Centre: Centre for Foundation Studies in Science, Universiti Malaya
Lecturer: Dr Siti Nabila Aidit (SNA)
Given Constants
- Permittivity of free space, $\varepsilon_0 = 8.85 \times 10^{-12} \text{ F m}^{-1}$
Question 1
An electric field of $2.80 \times 10^5 \text{ V m}^{-1}$ is desired between two parallel plates each of area $21.0 \text{ cm}^2$ and separated by $0.250 \text{ cm}$ of air.
Determine the charge on each plate.
Question 2
A parallel-plate capacitor has a dielectric made of Teflon that completely fills the space between the plates. Each plate has an area of $0.50 \text{ m}^2$. Dielectric constant for teflon is $2.1$.
Calculate:
a) What is the thickness of the teflon if the capacitance is to be $0.10 \mu\text{F}$? b) Calculate the charge on the capacitor if it is connected to a 12 V battery.
Question 3
A parallel-plate capacitor has plates with an area of $405 \text{ cm}^2$ and an air-filled gap between the plates that is $2.25 \text{ mm}$ thick. The capacitor is charged by a battery to 575 V and then is disconnected from the battery.
Calculate the energy stored in the capacitor.
Question 4
Three capacitors of $2 \mu\text{F}$, $3 \mu\text{F}$, and $4 \mu\text{F}$ are connected in series with a 6 V battery.
When the current stops flowing, calculate the potential difference across the $4 \mu\text{F}$ capacitor.
Question 5
An uncharged capacitor of $58 \mu\text{F}$ is connected in series with a resistor of $100 \text{ k}\Omega$ and a battery. Then the capacitor starts charging through the resistor.
Calculate the time required for the capacitor to reach 30% of its maximum charge.
Question 6
A fully charged capacitor has $12.0 \mu\text{F}$ and $6.0 \text{ mC}$. The capacitor has been discharged through a $100 \Omega$ resistor.
Determine:
a) Potential difference across the capacitor. b) The time constant for the discharging circuit. c) Find the time required for 80% of the charge to be discharged from the capacitor. d) Sketch $I-t$ graph to show the process.
Related Concepts
- Capacitors & Dielectrics
- Capacitor
- Capacitance
- Parallel Plate Capacitor
- Dielectric
- RC Circuit
- Time Constant
- Energy Stored in Capacitor
- Capacitors in Series
- Capacitors in Parallel