CHAPTER 19 - PHYSICS - ELECTRIC FIELDS

false

Dielectric materials are classified as electrical conductors. true false

true

Electric field lines are continuous from one charge to an opposite charge. true false

capacitor

It is a device used to store an electric charge. capacitor insulator

true

The farad is a very large unit of capacitance. true false

true

Two identical capacitors connected in parallel have double their individual capacitance. true false

ANSWER NASA PROBLEMS

Which of the following equations is used to find capacitance?

test charge

__ is a positive charge small enough that it does not distort an electrical field.

insulators.

Capacitor dielectrics are usually metals. semiconductors. insulators. conductors.

false

Electric fields are two-dimensional representations of electrical force. true false

true

Electrical potential energy (Ue) is the potential energy a charged object has by virtue of its distance from another charged object. true false

capacitor

Leyden Jar is a capacitor or insulator?

equipotential surface

___ is an imaginary surgace in an electrical fiel on which the electrical potential is the same at all points.

true

A capacitor consists of two conductors separated by a dielectric. true false

true

All objects are surrounded by their own gravitational fields of force. true false

an equipotential surface.

An area surrounding a charged object in which there is no change in electric potential is known as an electric field. a neutral ground. an equipotential surface. a capacitor.

farads

Capacitance is measured in volts per newton. ohms. joules per coulomb. farads.

true

Capacitors with a vacuum dielectric ( = 1) have the ability to tolerate much larger potential differences than capacitors with a Mylar dielectric ( = 3.1). true false

false

Lines of force can actually cross each other where electrical fields are exceptionally strong. true false

true

All forces have the potential to do work by exerting a push or a pull on an object and moving it. true false

false

An electric field has no directional character. true false

false

By convention, test charges for evaluating electric fields can be either positive or negative. true false

false

Capacitance is SI base units is Csquared / J. true false

false

Dielectric substances are usually good conductors. true false

true

Dielectrics are insulators and thus would not make good conductors. true false

false

Doubling the number of identical capacitors connected in series doubles the amount of charge that can be stored by the entire circuit. true false

true

Electric field lines terminate on negative charges. true false

is a vector quantity.

Electric field strength has no directional character. has only magnitude. is a scalar quantity. is a vector quantity. is neither a vector nor a scalar quantity.

ANSWER NASA PROBLEMS

Electric field strength is found by using which of the following equations?

true

Electric fields are generated in all three dimensions. true false

false

The electric field strength vector E is tangent to the field's lines of force and points toward the positive charge. true false

true

The sharper the curvature of an equipotential surface the more concentrated the lines of force. true false

false

The thicker the lead coating in a Leyden jar the greater the amount of charge that could be stored, assuming all other dimensions and materials were held the same. true false

true

The total capacitance is the sum of the individual capacitances. true false

true

To calculate the total capacitance when two or more capacitors are in parallel, just add the capacitance of the individual components. true false

use capacitors with plates that are closer together.

To increase the total capacitance of a circuit, arrange the capacitors in series. use a dielectric with a lower dielectric constant. use capacitors with a smaller surface area. use capacitors with plates that are closer together.

vacuum dielectric

What is the best insulator?

true

Within limits, the greater potential difference supplied to a capacitor, the greater the amount of charge that can be stored. true false

false

Doubling the number of identical capacitors connected in series doubles the capacitance of the circuit segment. true false

true

Doubling the plate area of a capacitor doubles its capacitance. true false

true

Michael Faraday is credited with developing the field model of forces. true false

false

The farad is a very small unit of capacitance.ue true false

false

Unlike gravitational potential energy, electrical potential energy's zero point is not taken to be an infinite separation between the charge source and the test charge. true false

capacitance

is the amount of charge per volt of potential difference that a capacitor can store.

electrical potential

As with gravity, when dealing with changes of position within an electrical field, only the differences in __________ ____________ are important.

true

Electric field lines represent the direction of the electric field. true false

true

Electrical potential energy's zero point is usually taken to be an infinite separation between the interacting charges true false

true

Electrical potential is analogous to gravitational potential. true false

true

Electrical potential is measured with reference to an infinite position from a charge. true false

true

Equipotential surfaces are imaginary constructs surrounding charged objects. true false

true

Every charged object is surrounded by an infinite series of 3D equipotential surfaces. true false

true

Every electric field line originates at a positive charge and terminates at a negative charge, even if the line is not visible beyond the edge of a diagram. true false

true

Every electrically charged object has a surrounding field (region of space) in which it exerts an electrical force. true false

true

Every magnetic object is surrounded by a magnetic field of force. true false

true

Field lines point in the direction that a small, positively charged object would move in response to the electric field. true false

true

Field model lines of force can show both the relative magnitude and direction of the field strength vectors. true false

true

Field strength is the rate of change of electrical potential with distance in an electric field. true false

true

If a capacitor has a large dielectric constant, then its ability to store charge for a given potential difference is large. true false

false

If a capacitor has a large dielectric constant, then its ability to store charge for a given potential difference is small. true false

true

If we connect several capacitors in parallel, the total capacitance will be more than if we connect them in series. true false

all of the above are true.

In a scanning tunneling electron microscope (STM), the needle tip ends at a single atom. the needle tip is given a positive charge. the electrons at the surface are attracted to the tip and can jump the vacuum gap by "tunneling." all of the above are true.

true

Like gravitational potential energy, electrical potential energy's zero point is usually taken to be an infinite separation between the charge source and the test charge. true false

show the direction of the electric force at each point in a field.

Lines of electric force show the direction of the electric force at each point in a field. are least numerous near concentrations of charge. originate at negative charges. are strongest halfway between two charges.

false

Lines of force, by convention, originate at the surface of the negatively charged body. true false

true

Lines of forces originate at the positively charged body. true false

true

Test charges are always positive. true false

to store charge.

The Leyden jar was invented to produce charge. to measure charge. to store charge. to provide a ground path for charge.

farad

The SI unit of capacitance is the farad. tesla. pascal. henry.

volt

The SI unit of electrical potential difference is the watt. amp. volt. ohm.

false

The capacitance of a vacuum dielectric capacitor is greater than for a capacitor of the same dimensions having a glass dielectric. true false

is tangent to the electric field line.

The direction of E is tangent to the electric field line. is perpendicular to the electric field line. points at the negative charge at all points in the field. points at the positive charge at all points in the field.

the force per unit of charge at each point in the field.

The electric field strength is directly proportional to the charge squared. measured in grams per coulomb. the force per unit of charge at each point in the field. measured in coulombs per newton. inversely proportional to the force.

true

The field model is an approach to explaining such three-dimensional phenomena as magnetic, electric, and gravitational forces. true false

true

The fundamental process of determining the direction of the electric field strength in an electric field involves vector addition of the electrical forces from all sources of charge at a point in space. true false

dielectric

The nonconductive substance separating the plates of a capacitor is called a resistor. dielectric. metal. dicapacitance.

work / move

The potential dfference between two points is the amount of ___ needed to ___ a unit charge between the points. work / move pressure / charge force / act

true

The potential difference (voltage) is the same in all areas of the circuit. true false

false

Very few charged objects are surrounded by infinite series of 3D equipotential surfaces. true false

parallel to the field lines and away from the charge

What direction does a test charge move when it is influenced by a positive charge? perpendicular to the field lines and toward the charge perpendicular to the field lines and away from the charge parallel to the field lines and toward the charge parallel to the field lines and away from the charge

capacitor current

Which of the following does capacitance not depend on? capacitor current capacitor charge distance between the capacitor plates capacitor dielectric

Lines of force are perpendicular to the electric field strength vector.

Which statement about electric lines of force is not true? Lines of force are perpendicular to the electric field strength vector. Lines of force point toward negative charges. The closer the lines of force, the stronger the electric field. Field lines never cross one another.

electrical potential (V)

___ is the amount of work per unit charge that is needed to move a charge a certain distance r from a point of charge. electrical potential energy (Ue) electrical potential (V)

dielectric constant

___ is the ratio of the charge of a capacitor with a dielectric compound to the charge of that capacitor with only a vacuum.

electrical potential energy (Ue)

___ the amount of work that is necessary to move a charged object from one point to another. electrical potential energy (Ue) electrical potential (V)

electric field strength or E

____ is the ratio of the electrical force one object exerts on another divided by the charge of the second object.

vacuum

A capacitor with a __________ dielectric has maximum field strength. glass air vacuum water

true

A capacitor with a larger surface area will have a higher capacitance than one with a smaller surface area. true false

true

A dielectric can conduct current if the potential difference across the material is large enough. true false

true

A flat-plate capacitor and a cylindrical, spiral-plate capacitor have the same capacitance if they have the same conductor and dielectric materials, cross-sectional areas, and distances between their plates. true false

true

A large dielectric constant implies that more charge can be stored for a given potential difference between the plates. true false

false

An electric field test charge is assumed to be a negative charge. true false

true

An electric field test charge is assumed to be a positive charge. true false