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COLLEGE PHYSICS PROBLEMS

 

1. In the diagram shown below:
a) Determine the electric potential at point P (with respect to infinity) due to the three charges shown.
b) Determine the work done moving a 8 uC charge from infinity to point P.

 

2. In the diagram shown below each charge is 5 uC; the distance L is 20 cm., and the electric field strength is 2000 n/c. Determine the dipole moment, the torque on each dipole, and the potential energy of each dipole with respect to the applied field.

 

3. Two large equally charged plates, shown below, form a parallel plate capacitor.
a). If the uniform part of the electric field between the plates (not near the plate edges) is 1000 n/c , determine the potential difference between the two plates.
b) If the cross sectional area of each plate is 2 m2, what is the charge on each place?

 

4. Two charged thin spherical shells are shown below. Q1 = + 50 uC, Q2 = - 80 uC, R1 = 20 cm, R2 = 40 cm.
a). Determine the Electric Potential at R =10 cm, R =30 cm, and R = 50 cm
b). Determine the amount of work needed to move a 5 uC charge from R = 40 cm to R = 20 cm.
[Hint: you need to find the electric potential at R=40 cm and R=20 cm first.]
c). Determine the amount of work needed to move a 5 uC charge from R = 20 cm to R = 0 cm.

 

5. An edge on view of three very large (infinite) sheets of charge are shown below. Sheet 1 has a charge density of +2 uC/m3, Sheet 2 has a charge density of -4 uC/m3 , Sheet 3 has a charge density of +6 uC/m3.
a). Determine the work done moving a 10 uC charge from plate 1 to plate 3 (assume you can pass through plate 2).
b). If the 10 uC charge had a mass of 50 grams and were placed at plate three and released, determine its velocity when it reached plate 2.
c). Determine its velocity when it reached plate 1.

 

6. If the expression for the electric potential at some region in space is V= 20 x2 –50 y + 30 z3 (Volts), then determine:
a). The expression for the electric field at that region in space.
b). The strength of the electric field at x =2 m, y = 5 m, z = -2 m.

 

Answers to Problems: 1a. 2.45 x 106 Volts, 1b. 19.6 J; 2a 1x10-6 c-m to right, 1x10-6 c-m @180o, 1x10-6 c-m @ 225o; 2b 2x10-3 n-m out of paper, 0, 1.414 x10-3 n-m into of paper; 2c 0, 2x10-3 J, 1.414 x10-3 J: 3a 100 V, 3b 1.77x10-8 C; 4a 450,000 Volts, -300,000 Volts, -540,000 Volts, 4b 5.625 J, 4c 0; 5a .9 J, 5b 6 m/s, 5c 6 m/s; 6a E = -40x i + 50 j -90z k, 6b E = -80 i + 50 j - 360 k, and magnitude E = 372 n/c.