07/13/07 Name, Roster # Physics 152 Midterm 1

Transcription

1 The figure to the right showing two positive point charges pertains to questions If q1 and q2 are the same amount of charge, which arrow best represents the direction of the net electric field at the point labeled A? 2. If q1 is twice as much charge as q2, which arrow best represents the direction of the net electric field at the point labeled A? 3. Starting from point A, if you move directly to the left, the electric potential will? a. increase b. decrease c. remain the same d. impossible to tell 4. An electron is initially placed at a point where the electric potential has a value of 200 V. The electron is then released. Later on, it is located at a position where the electric potential has a value of 250 V. What will the electron's kinetic energy be at this later time? a. 0 ev b. 50 ev c. 200 ev d. 250 ev e. 450 ev f. 50 J g. 200 J h. 250 J i. 450 J 5. A 20 gram particle with a net charge of is placed in a region where there is a constant electric field. The particle is released. It is observed that 3.0 seconds after the particle is released, it has a speed of 6.0 m/s. If the only force acting on the particle is the electric force, what is the magnitude of the electric field in this region of space? a N b N c N d N

2 The diagram below showing the configuration of two point charges pertains to questions Which arrow best represents the direction of the net electric field at point A? 7. What sign and magnitude of charge must be placed at point B such that the electric field at point A equals zero? a. +2 b. +4 c. +8 d. +16 e. +32 f. +64 g. -2 h. -4 i. -8 j. -16 k. -32 l What sign and magnitude of charge must be placed at point B such that the electric potential at point A equals zero? a. +2 b. +4 c. +8 d. +16 e. +32 f. +64 g. -2 h. -4 i. -8 j. -16 k. -32 l Two positively charged particles separated by a distance of d have an electric potential energy of 20 J. What would the electric potential energy be if the distance between the two charges was doubled? a. 5 J b. 10 J c. 20 J d. 40 J e. 80 J 10. In the figure shown to the right. if q1= +2.0 µ, q2=+4.0 µ and q3=+3.0 µ then what is the angle above the horizontal (i.e. θ in the diagram) of the net electrical force that acts on q3. (Note: Force shown on diagram is not precisely drawn) a. 18 b. 27 c. 34 d. 56 e. 63 f. 72

3 11. Two protons initially close to each other are released from rest and are completely free to move. After being released: a. Their kinetic energies gradually decrease to zero as they move apart. b. Their kinetic energies increase as they move apart. c. One of the protons kinetic energy will increase as the other protons kinetic energy decreases. d. The electric potential energy increases as the two protons move apart 12. Two particle of net charge +30 µ and -60 µ are separated by a distance d. If the electrical force acting on the +30 µ is 4.0 N due west, what is the magnitude and direction of the electrical force acting on the -60 µ charge? a. 2.0 N due west b. 2.0 N due east c. 4.0 N due west d. 4.0 N due east e. 8.0 N due west f. 8.0 N due east 13. Two unequal point charges are separated as shown in the figure. The electric field due to this combination of charges can be zero: a. Only in region 1 b. Only in region 2 c. Only in region 3 d. In both regions 1 and 3 The circuit shown below pertains to questions 14 and 15: 14. What is the total current (I t ) that flows in the circuit shown? a. 1.2 A b. 2 A c. 3 A d. 5 A e. 10 A 15. In the circuit shown, how much power is dissipated in the 6Ω resistor? a. 6.0 W b. 12 W c. 24 W d. 36 W e. 60 W

4 16. An electron is moving horizontally (to the right) in a laboratory when a uniform electric field is suddenly turned on. This field points vertically downward. Assuming that gravity can be neglected, which of the following paths will the electron follow? The following information pertains to questions 17-19: A capacitor (as shown) of capacitance is charged such that it has a net charge of +Q on its left plate and a net charge of -Q on its right plate. 17. What is the potential difference between the two plates? a. Qd b. Q/d c. /Q d. Q e. Q/ 18. If a particle of mass m and net charge +q is placed between the plates of the capacitor and released, what is the magnitude of the acceleration it will experience? a. qq dm b. dm qq c. Qq dm d. dm qq e. q Qdm f. Qdm cq 19. If the particle of mass m and net charge +q is placed between the plates of the capacitor and release, how long will it take to reach a speed of v? (Assuming of course it doesn't travel far enough to reach the right plate) a. vqq dm b. vdm qq c. vqq dm d. vdm qq e. vq Qdm f. vqdm cq 20. Which of the following statements is true? a. The electric field points from low V to high V b. A positive charge moving from high V to low V will slow down. c. A positive charge feels a force in the same direction as the electric field d. A negative charge moving from high V to low V will speed up

5 , Problem 1 a. In the circuit above using the given currents, label the polarities of all the resistors.[4 points] b. Using Kirchoff's voltage law, write the equation for loop A shown.[4 points] c. Given that I 1 =5A, find I 2.[4 points] d. Find I 3.[4 points] e. Find V B.[4 points]

6 , Problem 2 a. In the region between A and F above, in which direction does the electric field point?[5 points] b. In between which two adjacent points above is the electric field the strongest?[5 points] c. How much work is required to move a -6.0 m charge from point A to point E?[5 points] d. If a -6.0 m charge is initially at point A and shot to the right with an initial kinetic energy of 2.0 J, what will its kinetic energy be when it reaches point E? [5 points]