- Physics
- DIY kit
- Class 10 to 12
- Printed report included
Charging & Discharging of Capacitor Condenser Kit DIY with Board and Report for 12th Class Physics Educational Investigatory Project for School
Code B0DK25P5Q1
- Paid for and delivered by Amazon. The current price and the delivery date for your PIN code are shown there.
- Sold by Gurukul Technicals Institute, Delhi.
- Need a different topic, a custom version or a school order? Ask on WhatsApp.
In this project guide
DIY kit
About this kit
This DIY kit lets a student build and study the charging and discharging of a capacitor, one of the most important ideas in Class 12 electrostatics and circuits. The listing says it includes a board and a report. Watching the voltage rise and fall slowly makes the RC time constant easy to understand and to explain to an examiner.
How it works
The science behind it
The idea the kit demonstrates, in words you can use in your report and when you explain it.
A capacitor stores charge on two conductors separated by an insulator, with Q = CV. When it charges through a resistor R from a supply V0, its voltage does not jump at once; it rises as V = V0(1 − e^(−t/RC)). The product RC is the time constant τ, measured in seconds, because ohm × farad = second. After one time constant the capacitor reaches about 63% of V0, and after about five time constants it is practically full. On discharge through R the voltage falls as V = V0 e^(−t/RC), dropping to about 37% of its starting value after one τ. For example, 100 kΩ with 100 µF gives τ = 10 s, slow enough to time with a stopwatch. The energy stored is ½CV². The indicator LED on many adaptors and extension boards fades out a moment after switch-off because a capacitor inside is discharging through it.
Make it yourself
Make a capacitor charging and discharging circuit yourself
Everything you need and the order to do it in. Tick off the materials as you collect them.
What you need 8
Step by step 8 steps
Connect the capacitor and the 100 kΩ resistor in series, with the capacitor's striped (negative) lead to the battery negative.
Wire the two-way switch so one position connects the free end of the resistor to the battery positive (charge) and the other to the battery negative (discharge).
Connect the multimeter across the capacitor on DC volts.
Leave the switch on discharge until the meter reads zero, then flip it to charge and start the stopwatch.
Write down the voltage every 10 seconds until it stops rising, then flip to discharge and record the fall in the same way.
Plot both curves and mark the time at which the charging voltage reaches 63% of the battery voltage.
Repeat with another resistor and with the 470 µF capacitor, and compare the times you find.
For a visual demo, charge the capacitor, then let it discharge through the LED and its resistor and watch the light fade slowly.
Read this first
Safety first
Go through these points before you build or switch anything on. Younger students should do this with an adult.
- Always fit an electrolytic capacitor the right way round and use one rated above 9 V; reversed, it can swell or burst.
- Discharge the capacitor through a resistor before handling it, and never short its leads with a screwdriver.
- Use only the 9 V battery for this experiment.
- Disconnect the battery when you have finished your readings.
Troubleshooting
If something does not work
The usual problems with this kit and how to fix them. Open a problem to see the fix.
The voltage jumps to full straight away
The resistor is being bypassed or is very small. Check the circuit and use a larger resistor.
The voltage never quite reaches the battery voltage
The meter and a slightly leaky capacitor draw a small current, and the battery voltage drops with use. Measure the battery again and use that reading as the full value.
My measured time is different from R × C
Capacitors often differ from their marked value by 20% or more, and resistors by a few percent. This is a normal source of error to discuss in your file.
The LED does not glow on discharge
The capacitor may not be charged, or the LED is reversed. Charge it fully and check that the long leg goes to the capacitor's positive side.
Exhibition day
How to present it
A running order for the exhibition table or the practical, step by step.
Record the voltage every 5 or 10 seconds while charging and discharging, then plot both curves on graph paper.
Mark the 63% and 37% points on the graphs and show that both occur at about t = RC.
If you can swap the resistor or capacitor, change its value and show how the time constant changes; otherwise work it out on paper.
Discharge the capacitor fully before handing the board to anyone.
Practice
Viva questions
Practice questions on this kit, with short answers. Try each one aloud before you open the answer.
What is the time constant of an RC circuit?
It is τ = RC, the time in which a charging capacitor reaches about 63% of the supply voltage, or a discharging one falls to about 37% of its initial voltage.
Why is RC measured in seconds?
An ohm is a volt per ampere and a farad is a coulomb per volt, so their product is a coulomb per ampere, which is a second.
What is the energy stored in a capacitor?
U = ½CV², where C is the capacitance and V is the voltage across it.
Does current flow through the insulator of a capacitor while it charges?
No. Charge collects on the plates, and current flows only in the external circuit until the capacitor reaches the supply voltage.
Project file
Project file outline
The headings of the project file, in order. Give each heading its own section and write it in your own words.
The listing includes a printed project report: use this outline to check that your own file covers every part.
Free ebook: Writing a Science Project FileContents
- Aim: to study the charging and discharging of a capacitor through a resistor
- Capacitance and how a capacitor stores charge
- Circuit diagram and procedure
- Observation tables: voltage against time while charging and discharging
- Graphs of the charging and discharging curves
- Finding the time constant from the graph and comparing it with RC
- Uses: camera flash, timer circuits and smoothing in power supplies
- Sources of error and precautions
- Conclusion: how R and C together set the charging time, and references
Buying checklist
Before you buy
What to check before you order the kit, and what to do when it arrives.
1Before you order
- The listing says a board and a report are included; read the report and add your own readings and graphs to it.
- Check whether a battery and a multimeter are mentioned; arrange them if not.
- Do a full charge and discharge run at home before your viva so you know the timings.
- Keep the box and store all the components together.
- Check the delivery date for your PIN code on the marketplace, and order well before the exhibition or practical.
- Building it yourself: younger students should build with an adult, especially with motors, batteries and small parts.
2When it arrives
- On arrival, read the value and voltage rating printed on the capacitor's body.
Next steps
Take it further
Ways to turn this kit into a bigger investigation or a stronger exhibition entry.
Plot the natural logarithm of the discharge voltage against time; the straight line's slope gives the time constant.
Use a microcontroller to log the voltage every second and draw the curve automatically.
Connect two capacitors in series and then in parallel and compare their time constants with the formulas.
Audience
Who it suits
Class 12 physics investigatory projects on capacitors and RC circuits, and first-year engineering physics labs.
- ClassClass 10 to 12
- SubjectPhysics
- TypeDIY kit
- Project reportPrinted report included
Free to read
Free ebooks for this topic
Free PDF ebooks from Gurukul Technicals Institute on the science, the making and the presenting of projects like this one.
- Free PDF ebook
Physics Working Models Explained
Twenty classic models, how each works and how to make it
- Free PDF ebook
Investigatory Projects for Class 11 and 12
Topics, method and report structure for physics, chemistry and biology
- Free PDF ebook
Your Science Exhibition Guide
Choose a project, build it, present it and answer the judges with confidence
- Free PDF ebook
Writing a Science Project File
How to write the report, from the cover page to the bibliography
