Test No 1 Physics Carlos Medina-Hernandez Name: ID: Date

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Test No 1 Physics 1442-004 Carlos Medina-Hernandez Name: ID: Date Problem 1 ( worths 13% ) Three charges are arranged in the (x, y) plane (as shown below, where the scale is in meters).

1 Test No 1 Physics Carlos Medina-Hernandez Name: ID: Date Problem 1 ( worths 13% ) Three charges are arranged in the (x, y) plane (as shown below, where the scale is in meters). a) What is the magnitude of the resulting force on the 5 nc charge at the origin? b) What is the direction of the resulting force on the 5 nc charge at the origin? Provide an angle between 0 and 360 from the positive X axis counterclockwise direction

2 Test No 1 Physics Carlos Medina-Hernandez Name: ID: Date Problem 2 ( worths 13% ) From taking the same configuration as in problem 1 a) What is the magnitude of the resulting force on the 9 nc charge? b) What is the direction of the resulting force on the 9 nc? Provide an angle between 0 and 360 from the positive X axis counterclockwise direction

3 Test No 1 Physics Carlos Medina-Hernandez Name: ID: Date Problem 3 ( worths 12% ) Four charges are placed at the corners of a square in the following order :First Q1 then Q2 then Q3 and finally Q4. There is no charge in the center of the square a) find the magnitude of the electrostatic energy (U1) contribution for Q1 b) find the magnitude of the electrostatic energy (U2) contribution for Q2 c) find the magnitude of the electrostatic energy (U3) contribution for Q3 d) find the magnitude of the electrostatic energy (U4) contribution for Q4 e) Find the magnitude of the total electrostatic energy (Ut) of the system

4 Test No 1 Physics Carlos Medina-Hernandez Name: ID: Date Problem 4 ( worths 10% ) Two point charges of magnitude 8 nc and 4 nc are separated by 26.8 cm. What is the potential difference between a point infinitely far away and a point midway between the charges? Answer in Volts.

5 Test No 1 Physics Carlos Medina-Hernandez Name: ID: Date Problem 5 ( worths 10% ) A 20 V battery delivers 113 ma of current when connected to a 71 Ω resistor. a) Determine the internal resistance of the battery b) Find the power is dissipated by the 71 Ω resistor. c) Make a sketch of the circuit

6 Test No 1 Physics Carlos Medina-Hernandez Name: ID: Date Problem 6 ( worths 10% ) Four resistors are connected as shown in the figure. a) Find the resistance between points c and d. b) Find the resistance between points a and b.

7 Test No 1 Physics Carlos Medina-Hernandez Name: ID: Date Problem 7 ( worths 12% ) Consider the circuit shown : a) What equation does the loop DCFED yield? b)what equation does the loop DCBAD yield? c)what equation does the loop EFBAE yield? d) What equation does the node C yield?

8 Test No 1 Physics Carlos Medina-Hernandez Name: ID: Date Problem 8 ( worths 10% ) Find the value of the internal resistance

9 Test No 1 Physics Carlos Medina-Hernandez Name: ID: Date Extra Credit ( worths 10% ) A resistor CUBE: Find the R equivalent between A and B. Hint: Find and argument that allows you to reduce the circuit (explain)

10 Test No 2 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 4 th 2012 Problem 1 ( worths 20% ) A particle of mass M and charge Q Travels at a velocity V in a plane perpendicular to a Magnetic Field of magnitude B as shown in the Picture. Because of the Lorentz force the particle will experience motion on a circular path. (a) What is the plane of the circular path? (XY, XZ or YX) (b) Find the Radius of the circular path (show work) (c) is the particle moving clockwise or counterclockwise, Explain. (d) Find the time it will take to complete one full revolution.

11 Test No 2 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 4 th 2012 Problem 2 ( worths 20% ) Two wires are carrying currents of I and 3I in the direction out of the paper, they are apart by a distance L as shown in the figure. a) Find a point in between the wires where the total Magnetic field is equal to Zero. Give your answer in terms of L. b) Can you imagine another place where the magnetic field is equal to zero, Where?. Explain your Answer.

12 Test No 2 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 4 th 2012 Problem 3 ( worths 20% ) An infinite wire with weigh density λ1 (Kg/m) is suspended directly above another infinite straight wire with weight density λ2 (Kg/m.) The top wire carries a current of I1 (A) and the bottom wire carries a current of I2 (A). Take gravity as g. Find the distance of separation D between the wires so that the top wire will be held in place by magnetic repulsion.

13 Test No 2 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 4 th 2012 Problem 4 ( worths 20% ) A wire loop shaped as a square with sides 1 m lies in a plane perpendicular to a uniform magnetic field pointing from above into the plane of the loop, with a magnitude of 2 T. If in 5 s the wire is reshaped from a square into an equilateral triangle, but remains in the same plane, remember that all sides of equilateral triangle are the same length. (a) What is the magnitude of the area of the triangle? (b) What is the magnitude of the average induced emf in the wire during this time? (c) Is the direction of the current in the Loop during the deformation, clockwise or counterclockwise?. Explain your reasoning

14 Test No 2 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 4 th 2012 Problem 5 ( worths 20% ) Part of a rectangular coil with 250 turns of wire with dimensions shown in the figure is situated inside an external constant magnetic B = 0.5 T field in pointing inside the page, The total resistance of the wire is 250 Ω. And the velocity is v. (a) Start with Faradays Law of induction and demostrate that the emf also can be expresed as: emf = NBhv (b) Is the direction of the current in clockwise or counterclockwise? Explain your reasoning. (c) Calculate the magnitude of the current if h =1 m and v=10 m/s. (d) Calculate the force required to pull the loop from the field to the right at at constant velocity of 10 m/s. Neglect gravity.

Test No 2 Physics 1442-004 Carlos Medina-Hernandez Name: ID: Date: Apr 4 th 2012 Extra credit ( worths 10% ) (a) Use Amperes Law to find the magnetic field inside a toroidal

15 Test No 2 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 4 th 2012 Extra credit ( worths 10% ) (a) Use Amperes Law to find the magnetic field inside a toroidal coil (see figure) with N turns and curring a current I. (b) Use Amperes Law to find the magnetic field outside a toroidal coil (see figure) with N turns and curring a current I.

16 Test No 3 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 25 h 2012 Problem 1 An object is placed at at distance 1.5 f from a converging lens of focal length f, as shown. a) Follow the ray diagram rules to get an estimated position of the resulting image. b) Use the lens formula to calculate the image distance (answer in terms of f) c) find the lens magnification M

17 Test No 3 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 25 h 2012 Problem 2 A concave mirror with a radius of curvature of 1.0 m is used to collect light from a distant star. a) Make a diagram of the light rays and the mirror b) What is the distance between the mirror and the image of the star? c) Explain if this image is real or virtual

18 Test No 3 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 25 h 2012 Problem 3 A Ray of light traveling in air (index of refraction = 1) and it is incident at an angle of 61.9 on the surface of glass with index of refraction 1.52 a) What is the angle of refraction? Show work. b) What is the speed of light in the glass? Show work

19 Test No 3 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 25 h 2012 Problem 4 Start with the snell's law and show that the critical angle can be written as: c =sin 1 n 2 n 1 Show work

20 Test No 3 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 25 h 2012 Problem 5 A laser beam of wavelength nm is incident on two slits mm apart. The screen 6.22 meters apart. a) Find the angle of the first bright spot. Show work b) Find the angle of the first dark spot. Show work c) Find the distance in meters between these two spots. Show work

21 Test No 3 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 25 h 2012 Problem 6 The average lifetime of a pi meson in its own frame of reference (i.e., the proper lifetime) is s. If the meson moves with a speed of 0.66 c, what mean lifetime would be measured by an observer on Earth? Show work

22 Test No 3 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 25 h 2012 Problem 7 a) Find gamma for a particle moving with half the speed of light. Show work b) If the particle has a mass of one gram find its relativistic momentum. Show work

23 Test No 3 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 25 h 2012 Problem 8 Describe the photo electric effect. Can it be explained using classical physics? Why?

24 Test No 3 Physics Carlos Medina-Hernandez Name: ID: Date: Apr 25 h 2012 Extra credit (10%) A particle has an average lifetime T when at rest. In order for this particle to travel a distance L in the laboratory before it decays, how fast should it goes? In other words show that : v c = L L 2 c 2 T 2

Phys 2B Final Exam Name:

Phys 2B Final Exam Name: Multiple Choice (3 points each) 1. Two capacitors initially uncharged are connected in series to a battery, as shown. What is the charge on the top plate of C 1? a. 81 μc b. 18