AP Physics C: Chapters 23 & 24 Test

When a piece of paper is held with one face perpendicular to a uniform electric field the flux through it is 25 N × m²/C. When the paper is turned 25° with respect to the field the flux through it is:

• 0

• 12 N × m²/C

• 21 N × m²/C

• 23 N × m²/C

• 25 N × m²/C

•  $32\ N\cdot m^2/C$  

•  $34\ N\cdot m^2/C$  

•  $42\ N\cdot m^2/C$  

•  $48\ N\cdot m^2/C$  

•  $60\ N\cdot m^2/C$  

A point charge is placed at the center of a spherical Gaussian surface. The electric flux  $\Phi_E$  is changed if: 

• the sphere is replaced by a cube of the same volume 

• the sphere is replaced by a cube of one-tenth the volume

• the point charge is moved off center (but still inside the original sphere) 

• the point charge is moved to just outside the sphere 

• a second point charge is placed just outside the sphere 

Choose the INCORRECT statement:

• Gauss' law can be derived from Coulomb's law

• Gauss' law states that the net number of lines crossing any closed surface in an outward direction is proportional to the net charge enclosed within the surface

• Coulomb's law can be derived from Gauss' law and symmetry

• According to Gauss' law, if a closed surface encloses no charge, then the electric field must vanish everywhere on the surface

• Gauss' law applies to a closed surface of any shape

A physics instructor in an anteroom charges an electrostatic generator to 25  $\mu$ C, then carries it into the lecture hall. The net electric flux in  $N\cdot m^2$  /C through the lecture hall walls is: 

• 0

•  $25\times10^{–6}$  

•  $2.2\times10^5$  

•  $2.8\times10^6$  

• can't tell unless the lecture hall dimensions are given 

A particle with charge 5.0- $\mu$ C is placed at the corner of a cube. The total electric flux in  $N\cdot m^2/C$   through all sides of the cube is:

• 0

•  $7.1\times10^4$  

•  $9.4\times10^4$  

•  $1.4\times10^5$  

•  $5.6\times10^5$  

A point particle with charge q is at the center of a Gaussian surface in the form of a cube. The electric flux through any one face of the cube is:

• 
• 
• 
• 
• 

• 1, 2, 3, 4

• 4, 3, 2, 1

• 3, 4, 2, 1

• 3, 1, 4, 2

• 4, 3, 1, 2

A 3.5-cm radius hemisphere contains a total charge of 6.6 x 10^–7 C. The flux through the rounded portion of the surface is 9.8 x 10⁴ N × m²/C. The flux through the flat base is:

• 0

• $+2.3\times10^4N\cdot m^2/C$

• $-2.3\times10^4N\cdot m^2/C$

• $-9.8\times10^4N\cdot m^2/C$

• $+9.8\times10^4N\cdot m^2/C$

10 C of charge are placed on a spherical conducting shell. A particle with a charge of –3C is placed at the center of the cavity. The net charge in coulombs on the outer surface of the shell is:

• -7

• -3

• 0

• +3

• +7