Physics 196

Chapter 21-22-23

Practice exam

 

Sample Conceptual Problems: Do all 5 Problems. (2 points apiece)

 

1. Rank the following charges q₁ and distances,  by smallest to largest force on charge q₂

a). q₁ = 10micro coulombs at 1 meter

b). q₁ = 1 micro coulomb at 5 meters

c). q₁ = 2 micro coulombs at .5 meter

 b,c,a

2. Rank the following pair of charged objects by smallest to largest transfer of charge

a) A pair of 10 micro coulomb objects in contact

b) A 4 micro coulomb and 2 micro coulomb object in contact

c) A 5 micro coulomb and a 1 micro coulomb object in contact

 a,b,c

3. Rank the following by which charge will yield the largest E field at a distance of 1 meter

a). q = 12 micro coulombs

b). q = 1 coulomb

c). q = 5 micro coulombs

 c,a,b

4. Given a point charge of 100 micro coulombs, rank the following by increasing potential at the specified distance

(a). 25 cm                (b). 125 cm

(c). 65 cm                (d). 100 cm

b,d,c,a

 

5. The direction a charged particle moves in an electric field depends on:

(a) The magnitude of the charge.

(b)  The speed of the charge.

(c)  The polarity (sign) of the charge.

(d) All have an effect.

 c
 

 

Sample Low Difficulty problems: Do all 4 Problems (10 points apiece):

All work must be shown for full credit.

 

1. Determine the force on a 100 milli coulomb charge due to a 50 milli coulomb charge at a distance of 100 millimeters.

 4.495 x 10⁸ N

 

2. Determine the vector electric field due to a 50 micro coulomb charge at a point 50 cm from the charge.

 1.798 x 10⁶ N/C

3. Determine the acceleration of a 10 micro coulomb charge of mass 9.1 x 10^-31kg moving in an electric field of 2000 N/C.

 2.18 x 10²⁸ m/s²

4. A 45 micro coulomb charge is situated at the coordinates x = 0 and y = 4.5m. A second charge of 56 micro coulombs is situated at the coordinates x = 0 and y = 7.5 m. Determine the potential at the origin.

 1.55 x 10⁵ volts

 

Sample Advanced Difficulty Problems: Do all 4 problems. (25 points apiece).

All work must be shown for full credit!

 

1.  A 45 micro coulomb charge is situated at the bottom left corner of a square of length 1.0 meter.  A - 45 micro coulomb charge is situated at the bottom right corner. Determine the vector E field at the center of the top of the square.

 2.93 x 10⁵ N/C  i

2.  Determine the electric potential difference for moving a 100 micro coulomb charge from the point (r,q,f) = (0m, 0, 0) to a point (r,q,f) = (2.0m, p/3, p/6) against the electric field

 

E(r,θ,Φ) = r r² + (sin(θ) / r sin(Φ)) θ + (sin(Φ) / r) Φ

 

 - 3.3006 volts

3.  Determine the electric field for the potential function

 

    V(r,q,f) = r²sin q cos²f

 E (r,q,f) = - {[2r sin q cos²f] r + [r²(cos²f/sinf) cosq] q - [2r sinq cosf sinf] f}

 

4.

a). Use Gauss’ Law to determine the E field inside a solid sphere of radius R and volume charge density r(r)= Cr^2/3.

 E_inside = (12pC/44e_o)r^5/3

b). Determine the total charge contained within the sphere.