Problems for Physics 2020 recitation (week 4)1. The charge configuration shown below consists of 3 charges at 3 corners of a square withside length L.(a) What is the electric fi eld at the center of the square (point A)(b) What is the electric field at the 4th corner (point B)?(c) What is the electric potential at the center of the square (point A)(d) What is the electric potential at the 4th corner (point B)?(e) Given that Q = 1 µC and L = 1 cm, what is the magnitude of the acceleration on aparticle at point A with a mass of 1 kg and charge of 2 µC? How much work wouldbe required to move the particle from point A to point B?+Q+Q−2QBALL2. At the end of the first lab you were able to make a soda can move using a charged plasticrod. Explain how this works including n ecessary charge distributions and f orce diagrams3. A large conducting plate has a s urface charge density of +1 × 10−5C/cm2.(a) What is the voltage difference between a point 1 cm from th e plate and 10 cm fromthe plate?(b) What is the magnitude of the acceleration of a 1 g mass with +2 mC located 1 cmfrom the plate?(c) What is the magnitude of the acceleration of a 1 g mass with +2 mC located 10 cmfrom the plate?(d) If the 1 g, +2 mC mass is released from rest one centimeter from the plate, how muchkinetic energy will it have when it is 10 cm from the p late?4. A metal rod is resting on top of glass plate and is grounded via a wire. A positively chargedinsulated rod is brought close to the metal rod, the grounding wire is cut, and the rod isremoved.(a) Is there a charge on the metal rod before the insulated rod is b rought close?(b) Is there a charge on the metal ro d after th e insulated rod is removed? Is so, what isthe sign?5. Four balls hang from insulating nylon strings. Balls 1 and 2 attract, balls 1 and 4 repel,and balls 2 and 3 feel no force between them. Which balls are charged and of th e chargedballs, which have the same sign and which have opposite signs?16. A solid copper sphere with a radius of 5 cm has a net charge of +1 µC.(a) What is the electric field in th e center of the sphere?(b) What is the electric potential in the center of the sphere?(c) What is the electric field at a radius of r/2 from the center of th e sphere?(d) What is the electric potential at a radius of r/2 from the center of the sphere?(e) What is the electric field on the surface of the sphere?7. One charge is placed at the origin of the coordinate sys tem, the other one with the samecharge is placed at (5 m,0 m).(a) Are there positions where the electric field is zero? If so, find those special positions.If not, explain why.(b) Are there positions where the electric potential is zero? If so, find those special posi-tions. If not, explain why.8. Understanding electric fields and potential(a) What is an electric field? Try to explain in just words what a “field” is and why wemake use of this concept when we talk about electric forces.(b) What is electric potential? Here you can be a little more technical: What is the rela-tionship between electric potential and electric potential energy (you can supplementyour explanation with an equ ation if you so choose)? What is the relationship betweenelectric potential and the electric field at a point?9. There are the following charges on a line: 1 C at th e origin, 1 C at x = 2 m, and −2 C atx = 3 m . Find the coordinate(s) where the electric potential is
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