Physics Ch. 20-21

An area with excess electrons has a net ____ charge, an area with deficit of electrons has a net ___ charge a. negative, positive b. positive, negative c. positive, neutral d. negative, neutral

A

The unit ______ is used to measure work, whereas the unit ____ is used to measure electric potential difference. a. joule, volt b. volt, joule c. newton, volt d. newton, joule

A

Electric Field lines around a positively charged object extend: a. Towards the object b. Away from the object c. Both A and B d. None of the above

B

Electric forces are _________ forces, whereas frictional forces are ______ forces. a. contact, non-contact b. non-contact, contact c. frictional, real d. None of the above

B

The units used to measure electric field strength are: a. Joules/Coulomb b. Newtons/Coulombs c. Volts d. Coulombs

B

When two bodies are charged, the total charge before and after charging remains the same due to: a. quantization of charges b. conservation of charges c. law of induction d. Coulomb's Law

B

Which is a true statement about Electric Fields? a. Electric fields do not exist b. Electric fields are vectors c. Electric fields are measured in Coulombs d. Electric field have magnitude only

B

The direction of an electric field is: a. In the same direction as the force exerted on a negative test charge. b. Opposite the direction of the force exerted on a positive test charge. c. In the same direction as the force exerted on a positive test charge. d. Opposite the direction of the force exerted on a neutral test charge.

C

Which of the following is true about electric forces? a. Electric forces cause objects to only attract each other b. Electric forces cause objects to only repel each other c. Electric forces cause objects to repel or attract each other d. Electric forces do not exist

C

_______ is described as the ratio of an object's stored charge to its electrical potential difference

Capacitance

What is the name of the equation used to measure the size of the electrostatic force between two charged particles?

Coulomb's Law

unit for charge, electric field, electric potential energy, capacitance

Coulomb, N/C, J, Volt (J/C), Farad

_____ are strongest near the sharp points of sharply pointed conductors.

Electric fields

______ is described as the change in potential energy per unit charge in an electric field

Electric potential difference

The distance between two charges qa and qb is r, and the force between them is F. What is the force between them if the distance between them is doubled?

F/4

Which of the following is true for the direction of an electric field?

It is same as the direction of the force exerted on a positive test charge.

A/An_____ is a unit of energy, whereas a ______ is equal to one joule per coulomb

Joule, volt

A charged object will induce a separation of charges within a neutral conductor.

True

Like charges repel, whereas opposite charges attract.

True

Objects can be charged by the transfer of electrons.

True

One coulomb is the charge of 6.24 × 1018 electrons or protons.

True

Electric forces can be either repulsive or attractive, whereas gravitational force is always:

attractive

Electric field lines are directed _____ positive charges and ____ negative charges

away from, toward

Electric field lines are directed _____ positive charges and _____ negative charges.

away from, toward

The strength of the force on a charge in an electric field depends on

both magnitude of the field and size of the charge

A/An ______ is described as an electric device used to store charge, usually two conductors separated by an insulator

capacitor

Electric field strength depends on

charge and distance

Charging by _____ charges a neutral body by touching it with a charged body; whereas charging by _____ charges an object without touching it with a charged body.

conduction, induction

When two bodies are charged, the total charge before and after charging remains the same because of:

conservation of charges

What units do we use to measure electrical charge?

coulomb

A drop is falling in a Millikan oil-drop apparatus with no electric field. What are the forces acting on the drop, regardless of its acceleration?

drag force upward and gravitational force downward

An ________ exists around any charged object and alters the properties of the space around it

electric field

_______ provide a picture of an electric field indicating a field's strength

electric field lines

What change is observed in the strength of an electric field around a charged object if the magnitude of the test charge is doubled?

electric field remains unchanged

A/An _____ is a field that exists around a charged object, whereas _____ provide a model that indicate the field's strength.

electric field, electric field lines

______ are strongest near the sharp points of sharply pointed conductors

electric fields

_____ can act from great distances.

electric force and gravitational force

_____ and ________ can act from great distance

electric force, gravitational force

volt is a unit of

electric potential

The change in potential energy between two positions when work is done on a charge is called ________.

electric potential difference

What happens when a rubber rod is rubbed with a piece of fur, giving it a negative charge?

electrons are added to the rod

A device used for detecting charges that consists of a metal knob connected by a metal stem to two thin leaves is called a(n) ______________.

electroscope

The study of electric charges that can be collected and held in place is called _________.

electrostatics

The magnitude of the charge on one electron or one proton is called the __________.

elementary charge

In a capacitor, the two conductors have _____ charges

equal and opposite

In a capacitor, the two conductors have _____ charges.

equal and opposite

If the electric potential difference between two or more positions is zero, those positions are said to be ________________.

equipotential

Whenever the electric potential difference between two or more positions is zero, those positions are said to be _____.

equipotential

When a conducting sphere is charged positively, initially the charge is deposited on the left side. However, due to the sphere's conducting nature, the charge spreads uniformly throughout the surface of the sphere. Charge is uniformly distributed because:

excess electrons within the sphere move toward excess protons

__________ is the process of connecting a charged body to Earth to eliminate excess charge

grounding

Two equal point charges are separated by a distance d. when the separation is reduced to d/4 what happens to the force between the charges?

increases by factor of 16

Two charges are separated by a distance d. If one of the charges is doubled while the other is tripled, what happens to the force between the charges?

increases by factor of 6

The electric force between two charges is ___proportional to the square of the distance between them.

inversely

rubber rod rubbed with rabbit fur

negative

When the positive charge of the nucleus equals the negative charge of the orbiting electrons, the atom is said to be ____________.

neutral

glass rod rubbed with silk

positive

A difference between electrical forces and gravitational forces is that electrical forces include

repulsive interactions

Why is an electric field measured only by a small test charge?

so the charge doesn't disturb the field

Joules per unit Coulomb, or ________.

volt

When an electron is brought near a negatively charged sphere, its potential energy increases. The reason this happens is that

work was done to bring the charges together

What is the electric force in newtons between two charges, one of 1.8mC and the other of .004 C a distance 140cm?

8230.12 N/C

Two point charges are separated by 10.0 cm and have charges of +2.00 microC and -2.0 microC, respectively. What is the electric field at a point midway between the two charges? (k-sub e = 8.99 x 10^9 N x m^2/C^2)

4.4 x 10^6 N/C

A proton (+1.6 x 10^-19 C) moves 10 cm on a path in the direction of a uniform electric field of strength 3.0 N/C. How much work is done on the proton by the electrical field?

4.8 x 10^-20 J

How much energy does it require to move a constant positive charge of 2 C through a potential difference of 3 V?

6 J

An electron with a charge value of 1.6 x 10^-19 C is moving in the presence of an electric field of 400 N/C. What force does the electron experience?

6.4 x 10^-17 N

The electric field in a certain region of space is 20 N/C. What is the force on a 2C charge placed in that region?

60 N

Three rods of different materials P, Q, and R, are charged by various methods. When the rods are brought near each other, the rods P and Q repel each other, while the rods P and R attract each other. Which of the following could be the signs of the charges on the rods? Rod P Rod Q Rod R

- - +

What is the value of charge of a body that carries 20 excess electrons?

-3.20 * 10-18 C

Two point charges, initially 2 cm apart, are moved to 10 cm apart. By what factor does the resulting electric force between them change?

1/25

A 5 C charge is located near a positively charged sphere so that it has 50 J of electric potential energy. Its electric potential is

10 V

If you use 20 J of work to push a 2 C charge into an electric field, its voltage with respect to its starting position is

10 V

Two identical spheres each carry a charge of -40.0 microC. The spheres are separated by a distance of 1.00 m. What is the electric force between the spheres? (k-sub e = 8.99 x 10^9 N x m^2/C^2)

14.4 N repulsive

Two point charges, separated by 1.5 cm, having charge values of +2.0 microC and -4.0 microC, respectively. What is the value of the mutual force between them? (k-sub e = 9x10^9 N x m^2/C^2)

320 N