Physics II
zequet16
week_1-4.pdf
Week 1 Assignment
Electric Charges, Fields and Potentials
Please solve the following problems. You must show all work for full/partial credit.When
complete, attach a typed cover sheet and submit to the assignment drop-box.
1) An electron that is a certain distance from a proton is acted on by an electricalforce.
a) If the electron were moved twice the distance away from the proton, wouldthe
electrical force be:
1) 2
2) ½
3) 4
4) ¼
b) If the initial electric Force is, F, and the electron were moved to one third the
original distance toward the proton, what would be the new electrical force?
2) What is the magnitude and direction of the electric field at a point 0.75 m away from
a point charge of +2.0 pC?
3) Two fixed charges -4.0 C and -5.0 C, are separated a certain distance.
a) Is the net electric field at a location halfway between the two charges:
1) directed toward the -4.0 C charge
2) Zero
3) directed toward the -5.0 C charge
b) If the charges are separated by 20 cm, calculate the magnitude of the net
electric field halfway between the two charges.
4) What is the speed of a proton whose kinetic energy is 12.9 keV?
5) An electron is accelerated by a uniform electric field (1000 V/m) pointing vertically
upward. Use energy methods to get the magnitude and direction of its velocity after it
moves 0.10 cm from rest. Does the electron gain or lose potential energy?
6) How much charge flows through a 12 –V battery when a 2.0 uF capacitor is
connected across its terminals?
Week 2 Assignment
Electric Current and Circuits
Please solve the following problems. You must show all work for full/partial credit.
When complete, attach a typed cover sheet and submit to the assignment drop-box.
1) How long would it take for a net charge of 2.5 C to pass a location in a wire if it is to
carry a steady current of 5.0 mA?
2) Two copper wires have equal lengths, but the diameter of one is three times that of
the other.
a) The resistance of the thinner wire is _____ times that of the thicker wire:
(Prove your work)
1) 3
2) 1/3
3) 9
4) 1/4
b) If the thicker wire has a resistance of 1.0 , what is the resistance of the
thinner wire?
3) A 200 – W computer power supply is on 10 hours per day. If the cost of electricity is
$0.15/kWh, what is the cost (to the nearest dollar) to run the computer every day for a
year (365 days)?
4) What is the emf of a battery with an internal resistance of 0.15 if the battery
delivers 1.5 A to an externally connected 5.0 resistors?
5) Three resistors of value 1.0 , 2.0 and 4.0 are connected in a parallel circuit
with a 6.0 V battery.
a) What is the total equivalent resistance?
b) What is the voltage across each resistor and the current through each resistor
?
c) The power delivered to the 4.0 resistor?
6) What is the equivalent capacitance of two capacitors of 0.40 F and 0.60 F when
they are connected in:
a) series?
b) parallel?
7) Three capacitors of equal capacitance are connected in parallel to a battery, and
together they draw a certain amount of charge Q from that battery.
a) Will the charge on each capacitor be
1) Q
2) 3Q
3) Q/3?
b) Three capacitors of 0.25 F each in parallel connected to a 12- V battery.
What is the charge on each capacitor?
c) How much charge is drawn from the battery?
Week 3 Assignment
Magnetism and Induction
Please solve the following problems. You must show all work for full/partial credit.When
complete, attach a typed cover sheet and submit to the assignment drop-box.
1) If a charge particle move in a straight line and there no other forces on it
exceptpossibly from a magnetic field, can you say with certainty that no magnetic field
ispresent? Explain.
2) In a velocity selector, the uniform magnetic field of 1.5 T is produced by a
largemagnet. Two parallel plates with a separation of 1.5 cm produce the
perpendicularelectric field. What voltage should be applied across the plates so that:
a) A singly ionized ion traveling 8.0 x 104 m/s will pass through undeflected.
b) A double ionized ion traveling at the same speed will pass throughundeflected.
3) A horizontal magnetic field of 1.0 x 10-4 T is at an angle of 30o to the direction of the
current in a straight wire 75 cm long. If the wire carries a current of 15 A, what is the
magnitude of the force on the wire?
4) An electron travels at a speed of 2.0 x 104 m/s through a uniform magnetic field of
strength 1.2 x 10-3 T. What is the magnitude of the magnetic force on the electron if its
velocity and the magnetic field:
a) Are perpendicular
b) Make an angle of 45o
c) Are parallel
d) Are exactly opposite?
5) A square loop of wire with sides of length 40 cm is in a uniform magnetic field
perpendicular to its area If the field’s strength is 100 mT an it decays to zero in 0.010
seconds:
a) What is the magnitude and of the average emf induced in the loop?
b) What happens to the emf is the side lengths are reduced by a factor of ½?
6) The armature of an ac generator has 100 turns. Each turn is a rectangular loop
measuring 8.0 cm by 12 cm. The generator has a sinusoidal voltage output with an
amplitude of 24 V. If the magnetic field of the generator is 250 mT,
a) With what frequency does the armature turn?
b) If you double the B and cut in half, how does this affect the amplitude?
7) An ac generator supplies 20 A at 440 V to a 10,000 V power line. If the step up
transformer has 150 turns in its primary coil, how many turns are in the secondary coil?
Week 4 Assignment
Electromagnetic Waves and Light
Please solve the following problems. You must show all work for full/partial credit.
When complete, attach a typed cover sheet and submit to the assignment drop-box.
1) An antenna is connected to a car battery. Will the antenna emit electromagnetic
radiation? Why or why not? Explain.
2) A light-year is a measure of distance (not time). How many meters does light travel
in a year?
3) How long does it take a laser beam to travel to the Moon and back? Take the Earth
Moon distance to 384,000 km.
4) A beam of light is incident on a plane mirror at an angle of 35o. If the mirror rotates
through a small angle through what angle will the reflected ray rotate? DRAW a
diagram and note that the physical angle of the mirror change also changes the incident
angle. NOTE: An answer without drawing and proof will receive no credit for this problem.
5) The speed of light in polythene is 1.99 x 108 m/s What is the index of refraction of
polythene?
6) A beam of light with red and blue components of wavelengths 670 nm and 425 nm,
respectively, strikes a slab of fused quartz at an incident angle of 30o. On refraction, the
different components are separated by an angle of 0.001312 rad. If the index of
refractions of the red light is 1.4925, what is the index of refraction of the blue light?
Lab 1 Introduction
Lab 1 – Coulomb’s Law: Due at the end of Week 1
- Lab 1 Review textbook Chapter 16 which involves the vector nature of electric forces. In this simulation, the green, red, and blue charges are originally (i.e., at t = 0) at the vertices of an isosceles triangle. The green and blue are fixed in space and the red charge is allowed to move. Find the net Coulomb force (magnitude and direction) on the red object due to the green and blue charged objects after 1.00 s has elapsed.
This simulation can be downloaded from within your course under “PH221.Simulations”; its file name is “Net Coulomb Force.ip”.
Fill in the blanks in the Lab Answer Sheet at the end of this lab.
Submit this Lab Answer Sheet when all of the labs are completed.
These can be scanned and sent as pdf or picture files (e.g. tif, gif, etc.) or by any other method of your choice as long as the Answer Sheets are legible and translatable by Grantham University.
- Run the simulation. You will use the data from the “Time” and “Position” measurement tables (red, green, and blue) to help in calculating individual electrostatic (Coulomb) forces and directions.
Finally, calculate the net Coulomb force, Fc and direction, on the red object after 1.00 s; fill in the blanks on the Lab Answer Sheet to be handed in at the end of this week.
Lab 2 Introduction
Lab 2 – Ohms Law Due at the end of Week 2
Remember that Ohm’s Law states that
V = I R
Where V is the voltage, I is the current and R is the resistance. Also remember that now all materials are Ohmic.
Take these two sets of data and plot them.
Are they Ohmic? How can you determine this?
If they are Ohmic, what is the resistance of the circuit?
Data Set #1:
I (amps) V (volts)
0.1 0.5
0.2 1
0.3 1.5
0.4 2
0.5 2.5
0.6 3
0.7 3.5
0.8 4
0.9 4.5
1 5
1.1 5.5
1.2 6
1.3 6.5
1.4 7
1.5 7.5
1.6 8
1.7 8.5
1.8 9
1.9 9.5
2 10
Data Set #2:
I (amps) V (volts)
0.1 0.05
0.2 0.2
0.3 0.45
0.4 0.8
0.5 1.25
0.6 1.8
0.7 2.45
0.8 3.2
0.9 4.05
1 5
1.1 6.05
1.2 7.2
1.3 8.45
1.4 9.8
1.5 11.25
1.6 12.8
1.7 14.45
1.8 16.2
1.9 18.05
2 20
Lab 3 Introduction
Lab 3 – Mapping E field Lines Due at the end of
Week 3
- Lab 3 Review textbook Chapter 17 which involves mapping of E lines for a certain unknown charge distribution. Actually you will be mapping electrostatic (Coulomb) force lines since the electric field E is proportional to the Coulomb force by the equation (Equation 18.2) but these are equivalent to the E lines with equivalent directions and proportional magnitudes. This simulation can be downloaded from within your course under “PH221 Simulations”; its file name is “EXP #3 E FIELD #3.ip”.
- The direction of the electric field (or Coulomb force – Total Force in this experiment) is determined by placing a small + test charge, green in color throughout these simulations, near a charged configuration and noting the direction that the test charged is accelerated. You are free to move the small green test charge around to various locations, while noting (1) the exact location and (2) the direction of the force on that charge caused by all other charges. On the graph paper on your answer sheet, record the E field direction at the appropriate locations for the green test charge. Try to connect the arrows in a line to
form the electric field lines. These lines may not cross each other. For test charge locations, choose the corners of the squares all around the charged object(s).
Lab 4 Introduction
Lab 4 – Charged Object Moving in a Capacitor Due
at the end of Week 4
- Lab 4 Review textbook Chapter 19 which involves the vector characteristics of a moving charged object within a charged parallel plate capacitor. This simulation can be downloaded from within your course under “PH221 Simulations”; its file name is “#15 Charge and Cap.ip”. A positively charged particle is moving horizontally when it enters the region between the plates of a capacitor as the simulation illustrates. (a) Draw (sketch) the trajectory that the particle follows in moving through the capacitor. (b) When the particle is within the capacitor, which of the following four vectors, if any are parallel (||) to the electric field E inside the capacitor: the particle’s displacement (), its velocity (v), its linear momentum (p), and its acceleration (a)? For each vector, explain why the vector is or is not parallel to the electric field of the capacitor.
- Run the simulation noting the particle’s trajectory (as indicated by the “tracking” or “strobes”) while inside the capacitor cavity. Also note the velocity and acceleration vector, v and A, respectively arrows. Fill in the answers for the blanks in the Lab Answer Sheet at the end of this lab.
A capacitor is a charge storage device. A parallel plate capacitor consists of parallel conducting plates separated by an insulator. In this experiment, the insulator is air and there is equal but opposite charges (+Q and –Q) placed on each conducting plate (See Figure 18.25, Section 18.6 and 18.7 in your textbook). This virtual lab investigates the effects (if any) of a positively charged particle midway between the oppositely charged plates of a parallel plate capacitor moving in a + x-direction. Just as in Lab 3, there will exist an electrostatic (Coulomb) force on the charged particle when it is inside the capacitor.
In this lab, you will investigate electric field (E) lines. Electric charges create an electric field in space surrounding them. Electric field lines essentially give us a “map” of the direction and strength (magnitude) of the E field at various places in space. E lines are always directed away from positive charges and toward negative charges (see Figure 18.23, textbook Section 18.7, and Lesson 3). In Figure 18.27 the absence of E lines indicates that the electric field is relatively weak between the two positive charges. Since you will be performing in this experiment a virtual mapping of E lines for a certain charge distribution, carefully study Conceptual Example 13 (“Drawing Electric Field Lines”) for the dos and don’ts of mapping E field lines.
Electric Field Lines Mapping Rules -The E lines do not cross each other
-The closer the lines are together, the stronger the E in that region -The field lines indicate the direction of E; the field points in the direction tangent to the field line at any point -The lines are drawn so that the magnitude of the electric field, |E|, is proportional to the number of lines crossing unit area perpendicular to the lines. The closer the lines, the stronger the field -E lines start on + charges and end on - charges; the number starting or ending is proportional to the magnitude of the charge.
