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
