Electric Charges, Coulomb's Law, Extended Charged Objects

What is Electric Charge?

A property of objects that determines how they interact via electrostatic forces.

What is the nucleus of an atom made of?

Neutrons and protons.

What orbits around the nucleus of an atom?

Electrions

Macroscopic objects can become _______ by having more of either protons or electrons.

charged

“Like“ charges _____.

repel

“Opposite“ charges _______.

attract

What is a conductor?

A material through which charges can flow freely.

What is an insulator?

A material that is not a conductor.

Coulomb’s law enables us to find the electrostatic _____ between two charged particles.

force

Particles A, B, and C have the same charge. A is x distance from B, and C is 2x distance from B.

Compared to C’s electrostatic force on B, A’s electrostatic force on B is ____ as large.

4x

How do you find the total electrostatic force of a charged object on a particle with varying distance?

Take the integral of Coulomb’s law for every part of the object.

If the distance of every part of a charged object is the same from a charged particle, then we can find the total electrostatic force on the particle by…

Taking the sigma sum of Coulomb’s law for every part.

The electric field at a point is in the direction __________ to the line at that point.

tangent

The __________ of the electric field is proportional to the __________ of the field.

density, strength

Electric field lines never __________.

cross

Field lines in an electric field start at the __________ charges, and end at the __________ charges.

positive, negative

The number of lines at a charge is proportional to its amount of __________.

charge

Electric field diagrams should obey the __________ of the setup of charges.

symmetry

true/false

The field lines “try“ to spread out as much as possible from each other.

true

true/false

In an electric field diagram, if two charges have equal charge, then they must have the same number of field lines.

true

true/false

The net number of field lines in an electric field is dependent on the shape of the surface of an object.

false

The net number of field lines of an electric field only depends on the net __________ inside an object.

charge

__________ is the mathematical way to count field lines in an electric field.

Flux

To find the flux of an electric field that is not constant across the whole surface…

Integrate all small chunks of surface area of the object.

If all small chunks of surface area of an object are the same distance away from a point charge, then finding the flux involves…

Dividing the charge inside over epsilon_0.

When picking a useful Gaussian surface, what are the two rules you must follow?

Match the symmetry of the setup and make the point value where the E-field strength will be calculated reside on the Gaussian surface.

The E-field must obey the same __________ as the charge setup.

symmetry

The total flux of a surface which is parallel to the electric field is…

zero

Is the induced E-field inside a conductor weaker, stronger, or equal in strength to the external electric field?

Equal

The orientation of the induced electric field inside a charged object __________ __________ the external electrical field.

directly opposes

The work that will potentially get done by a force based on where the system starts and ends.

Potential Energy

__________ __________ is to potential energy, what electric fields are to force.

Electric potential

The Electric Potential V at a given point x is equal to…

The potential energy added to the system if +1C of charge were placed at x.

The potential energy due to charge q is equal to…

q * V

Where q is the charge, and V is the electric potential at the location of q.

Electric Potential is measured in Joules per Coulomb, otherwise known as…

Volts

true/false

Potential energy could be positive or negative.

true

A particle moves from charged region A to charged region B, starting from rest and reaching region B at a velocity v.

To describe the change in potential energy, we say that the particle has been __________ through a __________ __________ of |V_A - V_B| Volts.

accelerated, potential difference

The “Charge per Volt“ is also referred to as the…

Capacitance

The direction of force in an E-Field is __________ to lines of constant electric potential energy. (Similar to a topographical map around the charges representing the E-Field strength)

perpendicular

__________ are devices that allow use to stor

A simple example of a capacitor is the __________-__________ capacitor.

parallel-plate

The amount of charge something can store per Volt of potential difference refers to its…

Capacitance

Capacitance is measured in Coulombs per Volt, or in other words…

Farads

A parallel plate capacitor has a positive and negative plate inducing an electric field between the plates.

Directly between the plates, the E-field strength __________, travelling from the positive plate to the negative one. The E-field __________ everywhere else.

adds, cancels

The external E-Field is __________ to the surface of a conductor.

perpendicular

When inside an external E-Field, a conductor’s surface must be __________, that is, to have the same potential everywhere on its surface.

equipotential

Charge per second is known as…

current

What is Ohm's law?

Change in electric potential over resistance.

What does power output represent?

Rate which electric potential energy turns into other types of energy.