Key relationship
U=½CV²=Q²/(2C)=½QV.
Physics · Class 12
Capacitor energy
Energy resides in the electric field. A battery-connected dielectric insertion increases stored energy; inserting dielectric into an isolated capacitor decreases it.
Open the interactive experiment →Capacitor energy
தேக்கி ஆற்றல் மின்புலத்தில் சேமிக்கப்படுகிறது. U=½CV² என்பதால் மின்னழுத்தம் இரட்டிப்பானால் ஆற்றல் நான்கு மடங்கு.
Key notes, relationships and model limits
Remember
Energy resides in the electric field. A battery-connected dielectric insertion increases stored energy; inserting dielectric into an isolated capacitor decreases it.
Common trap
Use fixed Q or fixed V consistently when a dielectric or plate spacing changes; those constraints give different energy changes.
Model limits
The linear dielectric fills the entire parallel-plate gap. The readout is stored electric-field energy, with fixed voltage when connected and fixed charge when isolated; leakage and fringing are omitted.
What you will learn
Use the controls and plotted relation to explain capacitor energy.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
A 1 µF capacitor at 10 V stores 50 µJ; at 20 V it stores 200 µJ.
Why this matters
The model connects capacitor energy with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
For fixed C, doubling V changes stored energy by?
- A factor of two.
- A factor of four.
- A factor of one half.
Read the explanation
A factor of four.
Course connection: Class XII Chapter 2. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.