Topic: Electrostatic II
Sub Topic: Application of Capacitor
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:
Defined and Explain the work of a capacitor
Describe the charging and discharging of a capacitor
Appreciate simple designs/applications of capacitors.
- 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.
- 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.
- 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.
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.
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.
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
Size D dry cells, connecting wires, aluminium foil, various damaged electronic devices or circuits with capacitors.
Senior Secondary Physics. By P. N. Okeke and M. W. Anyakoha
full class session (5mins)
|Q/A on learners' prerequisite knowledge of capacitors||
||Learner’s entry points.|
|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|
|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|
|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.
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.|
|The teacher asks the students questions.
||Asking the learners questions to assess the achievement of the set objectives.|
|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.|