The Last Exercise
General Physics II
Due Date: 18/December/2019
Some Important Points:
I.
Do it in A4 paper and using pen!
II.
Answer the problem in order!
III.
The latest submission is 18/December/2019. After that the
task will not be graded!
IV.
This assignment is account as an additional point (if needed)
for your final exam and so do it maximally!
1. A current is flowing inside a 13 g wire with length 62 cm. Both ends is being
held with a spring with mass that can be neglected. The system immersed
inside a uniform and static magnetic field with direction into the page:
If the magnitude of the magnetic field is 0.44 T, determine the direction and
the magnitude of the current as to make the spring aren’t stretch!
2. Two infinite straight wire is carrying current. The first one I1 is located at x=a
and the second one I2 is located at x=-2a. If the magnetic field at x=0 is
vanishing, determine:
a. What should be the direction of I2?
b. The fraction between current in the first wire and the second wire!
3. An infinite wire carrying a current with magnitude 1 A is directed in the z
axis. An electron moving along with the current in the z axis with distance 1
m from the wire. Determine the vector force on the electron (that is express
in unit vector i, j, and k)!
4. An infinite wire carrying a current I. Besides this wire, a loop with width w
and length l as given in the picture below.
Determine:
a. The magnetic flux through loop due to an infinite wire!
b. If the current in the infinite wire are not static but I(t)=bt+I, where b is
some positive constant number, what will be the magnitude and the
direction of the emf induce on the loop!
5. A conductor rod with length l can move freely on a two parallel conductor
rods (blue rods) as in the picture below:
An external agent, push the rod with constant speed v and direction like the
picture. If on the two ends of the parallel conductors there is resistors with
resistance each R1 and R2, determine:
a. Current in both resistor and their direction!
b. Total power dissipated in each resistor!
6. A conductor in a form of circle is immersed inside non-static magnetic field
B(t)=B0+bt with B0 and b are positive constant.
a. Calculate the magnetic flux through the circle as a function of time!
b. Determine the initial value of the flux!
c. If the circle resistance is R, determine the current induce and its
direction!
d. At what rate the energy dissipates through the wire?
7. An RLC circuit with inductance 160 mH, capacitance 200µF, and resistance
40Ω connected to an AC source with voltage amplitude 40 V and angular
frequency 200 rad/s. Determine:
a. The impedance of the circuit!
b. Current on the circuit as a function of time and its phasor diagram!
c. Power dissipated from the system!
8. An AC source with emf 150 V and angular frequency 100 rad/s is connected
with 40Ω resistance, 80 mH inductance, and 50 µF capacitance as given in the
picture below:
a. Determine the voltage amplitude on the resitor, inductor and capacitor
each!
b. Potential between ab, bc, cd, ac, and bd!
c. The current on the circuit as a function of time!
9. An RLC circuit connected to the AC source that working on the resonance
state, with amplitude 200 V. If the resistance 20 Ω, capacitance 100 nF and
inductance 100 mH, determine:
a. Impedance of the system!
b. Current as a function of time, also draw its phasor diagram!
c. The root mean square of the emf and current!
d. Average power radiated from the circuit!
10. Two events are being observed by two observers A and B. The A observer,
see both events happen simultaneously with distance (between those events)
600 km while the B observer see both events separated by distance 1200 km.
Determine the speed of A according to B!
11. The lifetime of a muon at rest is 2.2 µs. From a cosmic ray, muon entering the
earth with speed 0.995c from the height 10 km above the ground. Determine:
a. Muon lifetime according to the observer on earth!
b. What is the time interval needed for the muon to reach the earth from the
perspective of observer moving along with the muon?
c. What is the time interval needed for the muon to reach the earth from the
perspective of observer on earth?
12. A particle A is at rest in a lab frame and disintegrate to two particles with the
same mass. Each moving in the opposite direction with the speed 0.67c to an
observer in a lab. Determine the speed of each particle measure by the
others!
13. Frame S’ moves relative to a frame S in positive x direction with speed 0.6c.
Frame S’ measured an object A to move in positive x’ direction with speed
0.4c. Determine:
a. What is the velocity of A relative to frame S?
b. What would be the velocity of A with respect to frame S if it moved at
0.4c in the negative x’ direction in the frame S’?
14. The energy needed to remove an electron from sodium metal is 2.8 eV. Does
sodium show a photoelectric effect for red light with wavelength 680 nm?
What is the cutoff wavelength for photoelectric emission from sodium?
15. The stopping potential for photoelectrons emitted from a certain surface is
found to be 0.71 V when illuminated from light with wavelength 491 nm.
When another wavelength is illuminated to this surface, the stopping
potential is found to be 1.43 V. Determine
a. The wavelength of this new incident light!
b. The work function for the surface!
16. What are the energy, wavelength and frequency of a photon that is emitted
by a hydrogen atom making a direct transition from an excited state n=5 to
the ground state?
17. A hydrogen atom is excited from its ground state to a state n=4. Calculate the
energy must be absorbed by the atom?
18. A hydrogen atom in a state having a binding energy (energy required to
remove an electron) of 0.85 eV makes a transition to a state with an
excitation energy (this is the difference in energy between the state and
ground state) of 10.2 eV. What is the energy of the emitted photon?
19. What is the frequency of a photon needed to unbound electron from a
hydrogen atom in a state n=8?
20. The same question as number 19 but with n=16? Which one is easier to
unbound and explain it?