Teacher Education

Teaching methods

Subject: Physics

Theme: Electrostatic

Topic: Electrostatic II

Sub Topic: Application of Capacitor

Date: dd/mm/yyyy

Class: S.S.S I

Duration: 35 Minutes

No of Learners: 30

Learning Objectives:

By the end of the lesson learners should be able to:
  1. Defined and Explain the work of a capacitor

  2. A capacitor is an electronic device that can store electrical charge.

    It can also be defined as an electric discharge resulting from the accumulation of electric charge on an insulated body.

    Working of a Capacitor: A capacitor consists of two metal plates that are separated by a non-conducting substance or dielectric. The metal plates are separated by a distance “d”, and a dielectric material is placed in-between the plates. The dielectric material is the main substance that helps in storing electrical energy.

  3. Describe the charging and discharging of a capacitor

  4. Charging of a Capacitor: If we connect a power source or a battery to the metal plates of the capacitor, a current will try to flow, or the electrons from the plate connected to the positive lead of the battery will start moving to the plate connected to the negative lead of the battery. However, because of the dielectric between the plates, the electrons won’t be able to pass through the capacitor, so they will start accumulating on the plate. This is called charging.

    Discharging of a capacitor: Now, if we shorten the two ends of the capacitor through a load, a current will start flowing through the load. The accumulated electrons from the first plate will start moving to the second plate until both plates become back again electrically neutral. This is called discharging.

  5. Appreciate simple designs/applications of capacitors.

    1. AC to DC Converter: A typical application example are capacitors used in DC adapters. For converting the AC voltage into a DC voltage a diode rectifier is usually used, but without the help of capacitors, it won’t be able to do the job. The output of the rectifier is a waveform. So while the output of the rectifier rises the capacitor charges, and while the output of the rectifier declines, the capacitor discharges and in that way smooth the DC output.
    2. Signal Filtering: Signal filtering is another application example of capacitors. Because of their specific response time they can block low-frequency signals while allowing higher frequencies to pass through. This is used in radio receivers for tuning out undesired frequencies and in crossover circuits inside speakers, for separating the low frequencies for the woofer and the higher frequencies for the tweeter.
    3. Capacitors as Energy Storage: Another rather obvious use of the capacitors is for energy storage and supply. Although they can store considerably lower energy compared to the same size battery, their lifespan is much better and they are capable of delivering energy much faster which makes them more suitable for applications where a high burst of power is needed.


Rationale:

Capacitors are part and parcel of electronic gadgets that are accessed and utilized basically in every home from where learners have grown. Today's learners are creative, critical and need to have a basic understanding of the gadgets they utilize. The lesson would enable learners to understand the use of capacitors, troubleshoot and even correct problems of capacitors in gadgets.

Prerequisite/ Previous knowledge:

Type and laws of charges, Current electricity flow, Mains Electricity, Electromagnetic Induction

Learning Resources:

Size D dry cells, connecting wires, aluminium foil, various damaged electronic devices or circuits with capacitors.

Reference Materials:

Senior Secondary Physics. By P. N. Okeke and M. W. Anyakoha

Lesson Development:

STAGE
TEACHER'S ACTIVITY
LEARNER'S ACTIVITY
LEARNING POINTS
INTRODUCTION
full class session (5mins)
Q/A on learners' prerequisite knowledge of capacitors
  • Law of charges: Things that have the same charge push each other away (they repel each other). This is called the Law of Charges. Things that have more electrons than protons are negatively charged, while things with fewer electrons than protons are positively charged. Things with the same charge repel each other.
  • Laws of charges:- Opposite charges attract each other. Like charges repel each other. Charged objects attract neutral objects.
  • Types of charges: There are two types of electric charge: positive and negative (commonly carried by protons and electrons respectively). Like charges repel each other and unlike charges attract each other. An object with an absence of net charge is referred to as neutral.
Learner’s entry points.
STEP 1
5mins.
Development
Distribute the devices and circuits to the learners and allow them to identify items marked. Receive reports Learners identify the device as a capacitor. Being able to isolate a capacitor from a circuit
STEP 2
15mins.
Teacher guide learners to inspect the capacitors and note down their capacitance. Learners inspect the capacitors and note down their capacitance. Reading capacitance of capacitors
STEP 3
20 mins
Guide the students to design a capacitor using available materials in the lab, test its storage and suggest how to improve the charge storage. Learners design a capacitor using available materials in the lab, test its storage and improve the charge storage. Being able to come up with a simple capacitor.
  1. Increase area of overlap
  2. Decrease the distance between the plates
  3. Dielectric material used
STEP 4
Group Work (5mins)
Guide the students to share any new things/activities they have discovered as a way to harmonize classroom activities. Learners share any new things/activities they have discovered. Maximum benefit to each participant from activities carried out.
EVALUATION
3mins
The teacher asks the students questions.
  1. From the activities carried out, what are a capacity and the working of a capacity?
  2. Explain the charging and discharging of a capacitor.
  3. Explain simple designs/ application of capacitors.
  1. A device for accumulating and holding a charge of electricity, consisting of two equally charged conducting surfaces having opposite signs and separated by a dielectric.
  2. A capacitor is a charge by connecting a power source or a battery to the metal plates of the capacitor. To discharge a fully charged capacitor, a load is connected across the two ends of the capacitor and the current will start flowing through the load. The accumulated electrons from the first plate will start moving to the second plate until both plates become back again electrically neutral.
  3. A capacitor is constructed out of two metal plates, separated by an insulating material called a dielectric. The plates are conductive and are usually made of aluminium, tantalum or other metals, while the dielectric can be made out of any kind of insulating material such as paper, glass, ceramic or anything that obstructs the flow of the current.
Asking the learners questions to assess the achievement of the set objectives.
CONCLUSION
2mins
Teachers wrap up from the learners' observations made in the group‟ activities. The students listen to the teacher and copy down notes. Consolidating and harmonizing scientific concepts.