PHYS 2 EXAM 2 (QUIZ QUESTIONS) UARK
The energy stored in a capacitor is equal to
( LOOK UP IN THE BOOK)
How can charge be moved?
(FIND THE ANS. IN THE BOOK)
Which of these is a property of current?
(LOOK UP IN BOOK)
The power dissipated by a resistor can be written as
(LOOK UP IN THE BOOK)
The resistance of a wire to current flow depends on
(LOOK UP IN THE BOOK)
The heart creates an electric dipole. How often does the orientation of the dipole change?
Every heart beat
What is the force on a charge Q in the electric field with strength E?
F=QE
Materials in which charges move easily are known as
Conductors
Electric fields are
Created by charged objects altering the space around them
A parallel plate capacitor
Creates a uniform electric field between two oppositely charged plates
What is the convention for the direction of charge flow in the context of electric current?
Current is the flow of positive charge
If a hollow conducting sphere has 10Mc of excess negative charge, what is the electric field inside the sphere?
0 N/C
The unit of electric potential is the volt. What is 1V equal to?
1 J/C
Video 2: What is the potential difference between a plate of a parallel plate capacitor and a point half way between the plates if the full potential difference between the plates is 5 V?
2.5 V
What is the typical potential difference and polarity across a cell membrane?
70 mV; inside more negative than outside
What is an electric dipole?
A neutral object with a separation between positive and negative charges
The electron volt is
A unit of energy
Which of the following materials has the highest dielectric constant? A. Water B. Barium Titanium C. Bakelite D. Quartz
A. Water
Electric fields Point from higher to lower potential Are perpendicular to equipotential lines Are stronger where the equipotential lines are closer together All of the above.
All of the above.
Which sequence describes how current is created?
An electric potential creates an electric field which creates the current
The author's analogy for a battery in a circuit is
An escalator
A charge of 1C is placed at the centre of a conducting sphere of a radius of 2 cm. What is the value of the electric field 1 cm from from the centre of the sphere?
Ans. 0 N/C
Two balloons with charges of +3.37 uC and -8.21 uC attract each other with a force of 0.0626 N. Determine the separation distance between the two balloons:
Ans. 2.80m
How are electric forces between several charged objects combined?
By adding the individual vectors.
The unit of capacitance, farad, F, is equal to
C/V
The unit of current is the ampere (amp) which is defined as
C/s
What is the difference between Coulomb's law for forces between charged objects and Newton's law of gravity?
Charge forces can be attractive or repulsive while gravity is only attractive.
What does the law of conservation of charge mean?
Charge is neither created nor destroyed when it is transferred.
What type of energy does a battery use to cause charges to move?
Chemical energy
As the distance between a proton and an electron increases, the electric force between them
Decreases
The electric potential in a charged parallel plate capacitor
Decreases from the positive plate to the negative plate
What are the charge carriers in a metal?
Electrons
The electrical potential at a resistor is
Higher at the end the current enters
How is the current, I, in a conductor related to the resistance, R, of the conductor and the potential difference across it, ΔV?
I = (ΔV)/R
Where is the energy stored in a capacitor?
In the electric field
What change would decrease the resistance of a wire?
Increase the cross-sectional area
The electric potential energy of 2 charged objects with the same sign charge
Increases as they are moved closer together
The capacitance of a capacitor can be increased by
Inserting an insulator between the plates
The force between an electron and proton
Is attractive
The energy stored in a capacitor
Is proportional to the potential difference squared
The equilibrium position of an electric dipole in an electric field
Is with the dipole moment in the same direction as the electric field
The electric potential inside a charged conductor in electrostatic equilibrium
Is zero
If you decrease the distance between two charged objects what happens to the force between them?
It increases
The potential energy of a charged particle in an electric field is proportional to
Its charge
What direction is the force on an electron in a uniform electric field pointing to the right?
Left
The resistivity of a good conductor is
Lower than insulators
What type of charge can move within a conductor?
Negative
When do electric field lines cross?
Never
Electric field vectors
Point toward negative charges and away from positive charges
What is the direction of the electric field in a charged parallel plate capacitor?
Positive to negative
What is needed in order for current to flow?
Potential difference and a complete circuit
A battery supplies which 2 things?
Potential difference and energy
Video 3: What is the source of the energy that made the foil ball bounce between the plates of the parallel plate capacitor?
Potential energy of the separated charges on the plates.
A lightning rod is intended to
Prevent a lightning strike by ionizing the air around it
The potential difference between plates of a parallel plate capacitor is
Proportional to the charge on the plates
In a circuit, how does the current before the resistor compare the current after the resistor?
Same before and after the resistor
A potential difference can be created by
Separating positive and negative charges
The capacitance of a parallel plate capacitor only depends on
The area of the plates and the distance between the plates
Video 2: What happens to the current in the Play-doh when the shape is changed so that it is longer and thinner?
The current decreases
Kirchhoff's junction law states
The current entering a junction is equal to the current exiting the junction
You measure a force F between 2 charged objects. What happens to that force if the charge on both objects is reduced to 1/2 of what is was?
The force is decreased by a factor of 4
A charged object moves freely in an electric field. As its electric potential energy decreases what can be said about its kinetic energy?
The kinetic energy increases
Which plate in a charged capacitor has the higher electric potential?
The positively charged plate
Each pair of leads used to make an electrocardiogram measure
The potential difference between the leads
Neutral objects have zero net electric charge because
There are equal amounts of positive and negative charge
How are the direction of electric field lines related to equipotential lines?
They are perpendicular
Capacitors are useful because
They can charge slowly and release the energy quickly
Which has a larger magnitude charge, proton or electron?
They have the same amount of charge, but opposite signs.
Video 1: When the current passed through 2 identical bulbs connected one after the other, which one was brighter?
They were the same
Electric field lines of a negative charge point
Toward the charge
What is the electric potential energy of 2 charge objects q1 and q2, when they are separated by a distance r?
U = K (q1*q2)/r
What direction is the force for on an electron due to earths electric field?
Up
The electric potential, V, of a point charge is related to the distance, r, from that charge as
V ∝ 1/r
Another term for the electrical potential difference between 2 points (like a battery) is
Voltage
What is true about the work, W, done on a book, and the change in gravitational potential energy, ΔU, of a book when you lift it at a constant speed?
W=ΔU>0
Electric field lines are closer together
When the electric field in stronger
In the model of an ideal wire in a circuit
Wires have 0 Ω of resistance
Does the shape of a charged conductor affect the electric field around it?
Yes. The field is stronger when it is at a point.
What is the electric field inside a conductor with a 2 nC of extra positive charges?
Zero
The electric field of a conductor with a 3 nC of excess positive charge
is perpendicular to the surface of the conductor
The electric potential energy of a charge q in terms of the electric potential, V, of the space around it is
qV
If you know the charge, Q, on a capacitor and the capacitance, C, what is the potential difference, ΔV?
ΔV = Q/C
