Chapter 23-worksheet 1. Estimate maximum the potential difference between a thundercloud and Earth, given that the electrical breakdown of air occurs at fields of roughly 3.0 106 V/m. (d=1000m) Ans: V-Ed, V=3.0 10 V 2. A point particle has a charge equal to +2.00 C and is fixed at the origin. (a) What is the electric potential V at a point 4.00 m from the origin? (b) How much work must be done to bring a second point particle that has a charge of +3.00 C from infinity to a distance of 4.00 m from the +2.00-C charge? Ans: (a) V=kQ/d, V=4.49kV (b) W=qV, W=13.5mJ 3. The facing surfaces of two large parallel conducting plates separated by 10.0 cm have uniform surface charge densities that are equal in magnitude but opposite in sign. The difference in potential between the plates is 500 V. What is the magnitude of the electric field between the plates? Ans: E-V/d, E=5kV/m 4. Three point charges are fixed at locations on the x-axis: q1 is at x = 0.00 m, q2 is at x = 3.00 m, and q3 is at x = 6.00 m. Find the electric potential at the point on the y axis at y = 3.00 m if (a) q1q2=q3= +2.00 C, (b) q1 = q2 = +2.00 C and q3 = -2.00 C, and (c) q1q3=+2.00 C and q2 = -2.00 c. Ans: (a) V=kq1/d+kq2/d+kq3/d, V=12.9kV (b) V=7.55kV (c) V=4.43kV 5. Three point charges are on the x-axis: q1 is at the origin, q2 is at x = +3.00 m, and q3 is at x = +6.00 m. Find the electrostatic potential energy of this system of charges for the following charge values: (a) q1 = q2 = q3 = +2.00 C; (b) q1 = q2 = +2.00 C and q3=- 2.00 C; and (c) q1 = q3 = +2.00 and q2 = -2.00 . Ans: (a) PE=kq1q2/d12 + kq1q3/d13 + kq2q3/d23, PE=30mJ (b)PE -5.99mJ (c) PE=-18mJ When 5.0 C of charge moves at constant speed along a path between two points 6. differing in potential by 12 V, the amount of work done is Ans: V = W/q, V=60J 7. 8. A uniform electric field exists between two parallel plates separated by 2.0 cm. The intensity of the field is 15 kN/C. What is the potential difference between the plates? Ans: V Ed, V=300V Two protons in a nucleus of 238U are 6.0 10-15 m apart. The electrostatic potential energy of the pair is approximately Ans: PE=kq1q2/d, PE= 3.8x10-14J Two charges Q1 (= +6 C) and Q2 (=-2 C) are brought from infinity to positions on the x-axis of x=-4 cm and x = +4 cm, respectively. How much work was done in 9. bringing the charges together? Ans: W= PE=kq1q2/d, W=-1.35J