10TH GRADE · ELECTROSTATICS

Capacitors

Electrical capacity, flat capacitor, energy and connections.

28 minutes13 theory cards

LESSON MATERIAL

Basic Concepts

A system of conductors designed to store electrical charge and field energy.

Equal opposite charges accumulate on its plates, and energy is stored in the electric field between them.

A connection in which adjacent plates form intermediate nodes without external branches.

All capacitors have the same charge, the voltages add up, and the equivalent capacitance is less than any individual capacitance.

A connection in which plates of the same name are connected to common nodes.

The voltage on all branches is the same, the charges add up, so the equivalent capacitance is equal to the sum of the capacitances.

LESSON MATERIAL

C

The ability of a conductor or capacitor to store charge at a given voltage.

Unit: farad · $\mathrm{F}$

S

The area of the overlapping part of the capacitor plates.

Unit: square meter · $\mathrm{m}^2$

W

Electric field energy of a charged capacitor.

Unit: joule · $\mathrm{Dzh}$

LESSON MATERIAL

C=\frac{q}{U}

Electrical capacity is equal to the charge per unit voltage.

1\,\mathrm{F}=1\,\frac{\mathrm{Kl}}{\mathrm{V}}

One farad corresponds to a charge of one coulomb at a voltage of one volt.

C=\frac{\varepsilon_0\varepsilon S}{d}

The capacity increases with area and permeability and decreases with the distance between the plates.

W=\frac{CU^2}{2}=\frac{q^2}{2C}

The energy of a charged capacitor is expressed in terms of capacitance, voltage or charge.

q_1=q_2=q,\quad U=U_1+U_2

Capacitors connected in series have equal charges, and the voltages add up.

\frac{1}{C}=\frac{1}{C_1}+\frac{1}{C_2},\quad C=\frac{C_1C_2}{C_1+C_2}

The reciprocal of the total capacity is equal to the sum of the reciprocal capacities.

C=C_1+C_2,\quad q=q_1+q_2,\quad U=U_1=U_2

When connected in parallel, the capacitances and charges add up, the voltage is the same.

PRACTICE