PHY02_CO2: ELECTRIC POTENTIAL ENERGY

Electric/Electricity

use as secondary energy source because it is produced by converting primary sources of energy into electrical power.

Electric Potential Energy

It is the energy that is needed to move a charge against an electric field.

Potential Energy

Stored energy that depends upon the relative position of various parts of a system. Can be converted to kinetic energy.

Formula: Work done by the gravitational force

Wab=mgh(a)-mgh(b)=GPE(a)-GPE(b)

Work done by the gravitational force

The work done by the electric force equals the difference beween the electrical potential energy EPE at point A and the electric potential energy at point B.

Electric Potential Difference

The electric potential V at a given point is the electric potential energy EPE of a small test charge q situated at that point divided by the charge itself

Formula: Electric Potential Difference

V=EPE/q; J/C=Volt(V)

Charges: Electric Potential Difference

For a positive charge, lower potential energy means lower potential, but for a negative charge, lower potential energy means higher potential.

Electric Potential Difference by Point Charge

The electric potential is higher (uphill) at A and lower (downhill) at B.

This result is valid whether q is positive or negative, and whether q₀ is positive or negative.

Formula: Electric Potential Difference by Point Charge

V=kq/r; k=8.99×10^9Nm²/C²

Equipotential Surfaces

- equal potential differences

- is a surface on which the electric potential is the same everywhere, given that it is on the same surface.

- The larger the distance r, the smaller is the potential of the equipotential surface.

- The net electric force does no work as a charge moves on an equipotential surface.

ADDITIONAL: Equipotential Surfaces

- the electric field is outward and the lines must always be perpendicular (90)

- distance is inversely proportional to the voltages

- if there’s electric dipole, V=constant

FORMULA: Capacitance of a Capacitor

q=CV; C=C/V=Farad(f)

Capacitance of a Capacitor

The region between the conductors or plates with an electrically insulating material called a dielectric.

The magnitude q of the charge on each plate of a capacitor is directly proportional to the magnitude V of the potential difference between the plates

Dialectric

Insulating material

To avoid the flow of charges

To have electric field between the two parallel plates for us to store electric energy

Capacitance

Tell us the ability of the capacitor to store energy

Application: RAM Chip

A single RAM chip often contains millions of such transistor–capacitor units. The address line is used by the computer to locate a particular transistor–capacitor combination, and the data line carries the data to be stored.

Michael Faraday

English physicist and chemist whose many experiments contributed greatly to the understanding of electromagnetism.

In 1831 he succeeded by using two coils of wire wound around opposite sides of a ring of soft iron.

He also demonstrated that an electric current can be induced by moving a magnet, by turning an electromagnet on and off, and even by moving an electric wire in Earth’s magnetic field. Within a few months, Faraday built the first, albeit primitive, electric generator.