Problem Based on Energy stored in Capacitor

Nowadays, everyone has a smartphone, It became an important part of our life.

We use a smartphone by touch on its screen to operate its function.

Its touchscreen is capacitive, means it uses several capacitors.

Which we operate with fingers.

All memory systems, including smartphones and all computers, use capacitors for binary memory systems.

A capacitor is a passive two-terminal electronic component that stores electrical energy in an electric field.

So, we are interested to discuss energy stored in the capacitor.

Next, we will solve a problem based on energy stored in the capacitor.

Let's solve a problem based on the energy stored in the capacitor.

Let's take a parallel plate capacitor of capacitance .

Now, we connect this to the power supply of .

Now again, a dielectric constant 5 is inserted into the gap between the plates.

Now, we want to find the extra charge flown through the power supply and the work done by the supply.

And we want to also find the charge in the electrostatic energy of the electric field in the capacitor.

We know after inserting the dielectric the capacitance will be changed.

So, charge stored in the capacitor is given by,

And work done by the supply is given by the equation,

The energy stored in the capacitor is given by,

As given in the problem the original capacitance was 100µF.

The charge on the capacitor before the insertion of the dielectric was

After the dielectric slab is inserted, the capacitance is increased to .

The new charge on the capacitor will be .

The charge flown through the power supply is, therefore .

Hence, we get the value of workdone by power supply that is .

Now, we have to find the change in the electrostatic energy in the capacitor.

Here, first we will calculate the electrostatic field energy of the capacitor.

The electrostatic field energy without the dielectric slab that is .

And the electrostatic field energy after the slab is inserted.

Thus, the energy is increased by .

Revision

A capacitor is a passive two-terminal electronic component that stores electrical energy in an electric field.

Formula to find energy stored in the capacitor.

Formula to find work done by the power supply.

Formula to find charge stored in the capacitor.

The End