PHYS 1120 Fall 2025 Exam 1 TEST VERSION A Name Student ID Turn off and put away your phone and smartwatch Please do not open the exam until you are asked to Check each box as you complete the instructions Clearly print your full name and student ID number above on this booklet Clearly print your full name and student ID number on your bubble sheet Bubble in version A on your bubble sheet Please circle your tutorial section below and sign the honor code pledge Show all your work and circle your answers on this exam booklet Failure to do so may result in a zero grade on the exam Your circled answers and bubbled answers must agree On your bubble sheet use pencil erase mistakes thoroughly and make no extraneous marks When you finish turn in both your exam booklet and your bubble sheet Then pick up a new bubble sheet for the group exam and then return to your seat Recitation Section and Time Sec 414 11 15 12 05 TA Name Ben Bobell Sean Driskill Matthew Fox Johnny Gallagher Henry Jordan Jiazheng Li Yun Ma Joe McCarty Maxime Pindrys Johannes Reinking Katherine Slattery Matthew Steele Sec 406 9 05 9 55 Sec 419 12 20 1 10 Sec 429 3 35 4 25 Sec 418 12 20 1 10 Sec 417 12 20 1 10 Sec 401 8 00 8 50 Sec 407 9 05 9 55 Sec 403 8 00 8 50 Sec 428 2 30 3 20 Sec 405 9 05 9 55 Sec 402 8 00 8 55 Sec 412 10 00 11 00 Signature Sec 410 10 10 11 00 Sec 434 4 40 5 30 Sec 423 1 25 2 15 Sec 421 1 25 2 15 Sec 408 9 05 9 55 Sec 432 3 35 4 25 Sec 411 10 10 11 00 Sec 430 3 35 4 25 Sec 409 10 10 11 00 Sec 420 12 20 1 10 Sec 416 11 15 12 05 Sec 431 3 35 4 25 Sec 425 2 30 3 20 Sec 426 2 30 3 20 Sec 435 4 40 5 30 Sec 415 11 15 12 05 Sec 433 4 40 5 35 Sec 413 11 15 12 05 Sec 422 1 25 2 15 Sec 424 1 25 2 15 Sec 427 2 30 3 20 By handing in this exam you agree to the following statement On my honor as a University of Colorado Student I have neither given nor received unauthorized assistance on this work Exam 1 cont 2 of 10 The exam consists of 22 multiple choice questions worth a total of 100 points Allowed material Hand written equation sheet one piece front and back of letter sized paper pencils and erasers Calculators are allowed but phones and smart watches are not and must be turned off and put away Note In all questions unless otherwise stated neglect air resistance and assume all wires and batteries are ideal Also unless otherwise stated assume all light bulbs and resistors are Ohmic Possibly useful information g 9 8 m s2 e 1 60 10 19 C k 8 99 109 N m2 C2 0 8 85 10 12 C2 N m2 me 9 11 10 31 kg Physics 1 Equations Fnet m a v v0 a t 1 2 x v0 t v2 v2 0 2a x F d r WF a t 2 The last page of this booklet is for scratch work Version A Exam 1 cont 3 of 10 0 1 Ensure that you have printed your full name and student ID number with clear and neat handwriting on both the front page of this exam AND on your bubble sheet Your student ID number is not written on your BuffOne Card Bubble in version A on your bubble sheet Failure to follow these instructions may result in the loss of one point on this exam Far from a point charge you measure an electric field of magnitude 800 N C If you double your distance from the point charge what will be the magnitude of the electric field at your new location A B C D E 800 N C 400 N C 200 N C 100 N C 50 N C 2 An initially neutral electronics worker walks across a carpet as a result the worker collects a net charge buildup of 6 4 10 18 C How many total electrons did they gain or lose A B C D E They gained 40 electrons They lost 40 electrons They gained 6 4 10 18 electrons They lost 6 4 10 18 electrons They lost 9 8 1035 electrons 3 A solid conducting metal sphere which is electrically neutral is held fixed in space A negative charge q is placed nearby outside the sphere as shown What is the direction of the electric field at point P inside the sphere halfway between the center and the edge of the sphere P just represents a point in space not a charge A B C D E No direction the electric field is zero Right Left Down Some other direction 4 Consider the three uniform infinite sheets of charge with the charge densities shown below All charge densities are the same magnitude Which set of arrows best represents the net electric fields at points A B and C Version A Exam 1 cont 4 of 10 5 In the two cases shown a central charge q has two charges of equal magnitude Q lo cated an equal distance above and below it In Case A the signs of the two outer charges are both positive and in Case B they are op posite You are not told the sign of the charge q in the center In which Case is the magni tude of the net force on the center charge q greater Case A Case B It depends on the sign of q Both Case A and Case B have the same magnitude net force A B C D A B C D E 0 kQ 2L2 2 2kQ L2 2 2kQ L2 2kQ L2 A B C Frod Fball Frod Fball Frod Fball Version A 6 Four charges are arranged at the corners of a square as shown What is the magnitude of the net electric field at the center of the square The cover page has some useful trig 7 In case A a point charge Q is a distance s from the center of from the center of a uniformly charged teflon rod with a total charge Q In case B the Q point charge is a distance s from the center of a small teflon ball with charge Q How does the net force on the rod in Case A rod compare to the net force on the ball in Case B ball Exam 1 cont 5 of 10 8 A thin rod of length L carries a negative charge Q distributed uniformly along its length It sits along the y axis with one end at the origin Which equation describes the net electric field due to this rod …
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