Exam 19: Electric Forces and Electric Fields

Two planes of charge with no thickness,A and B,are parallel and vertical.The electric field in region I to the left of plane A has magnitude $\frac { 3 \sigma } { 2 \varepsilon _ { 0 } }$ and points to the left.The electric field in the region to the right of B has magnitude $\frac { 3 \sigma } { 2 \varepsilon _ { 0 } }$ and points to the right.The electric field in the region between the two planes has magnitude $\frac { \sigma } { 2 \varepsilon _ { 0 } }$ and points to the right.The surface charge density on planes A and B respectively is

A point charge +Q is located on the x axis at x = a,and a second point charge -Q is located on the x axis at x = -a.A Gaussian surface with radius r = 2a is centered at the origin.The flux through this Gaussian surface is

Charge of uniform density (20 nC/m²)is distributed over a cylindrical surface (radius = 1.0 cm),and a second coaxial surface (radius = 3.0 cm)carries a uniform charge density of -12 nC/m².Determine the magnitude of the electric field at a point 2.0 cm from the symmetry axis of the two surfaces.

Two imaginary spherical surfaces of radius R and 2R respectively surround a positive point charge Q located at the center of the concentric spheres.When compared to the number of field lines N₁ going through the sphere of radius R,the number of electric field lines N₂ going through the sphere of radius 2R is

Enrico says that positive charge is created when you rub a glass rod with silk,and that negative charge is simply the absence of positive charge.Rosetta says that negative charge is created and that positive charge is the absence of positive charge.(She has heard that Ben Franklin should have reversed the signs he associated with the charges. )Which one,if either,is correct?

A Geiger counter is like an electroscope that discharges whenever ions formed by a radioactive particle produce a conducting path.A typical Geiger counter consists of a thin conducting wire of radius 0.002 cm stretched along the axis of a conducting cylinder of radius 2.0 cm.The wire and the cylinder carry equal and opposites charges of 8.0 *10 ^{- 10} C all along their length of 10.0 cm.What is the magnitude of the electric field at the surface of the wire?

Which one of the following is not an expression for electric charge?

Charge of uniform density (0.30 nC/m²)is distributed over the xy plane,and charge of uniform density (-0.40 nC/m²)is distributed over the yz plane.What is the magnitude of the resulting electric field at any point not in either of the two charged planes?

If Q = 25 $\mu$ C,q = 10 $\mu$ C,and L = 40 cm in the figure,what is the magnitude of the electrostatic force on q?

A charge Q is placed on the x axis at x = +4.0 m.A second charge q is located at the origin.If Q = +75 nC and q = -8.0 nC,what is the magnitude of the electric field on the y axis at y = +3.0 m?

A proton moving at 3 * 10⁴ m/s is projected at an angle of 30 $\degree$ above a horizontal plane.If an electric field of 400 N/C is directed downwards,how long does it take the proton to return to the horizontal plane? (HINT: Ignore gravity. )[m_Proton = 1.67 *10 ^{- 27} kg,q_Proton = +1.6 *10 ^{- 19} C.]

Identical point charges Q are placed at each of the four corners of a 3.0 m * 4.0 m rectangle.If Q = 40 $\mu$ C,what is the magnitude of the electrostatic force on any one of the charges?

When a positive charge q is placed in the field created by two other charges Q₁ and Q₂,each a distance r away from q,the acceleration of q is

Two tiny metal spheres are fixed to the ends of a non-conducting string of length $\ell$ .Equal charges,+q,are placed on the metal spheres.Randall says that the force on the string has magnitude $\frac { 1 } { 2 \pi \varepsilon _ { 0 } } \frac { q ^ { 2 } } { \ell ^ { 2 } }$ .Tilden says that the tension in the string has magnitude $\frac { 1 } { 2 \pi \varepsilon _ { 0 } } \frac { q ^ { 2 } } { \ell ^ { 2 } }$ .Which one,if either,is correct?

A positive point charge q is placed at the center of an uncharged metal sphere insulated from the ground.The outside of the sphere is then grounded as shown.Then the ground wire is removed.A is the inner surface and B is the outer surface.Which statement is correct?

Three point charges,two positive and one negative,each having a magnitude of 20 $\mu$ C are placed at the vertices of an equilateral triangle (30 cm on a side).What is the magnitude of the electrostatic force on one of the positive charges?

Two identical pith balls supported by insulating threads hang side by side and close together,as shown below. One is positively charged;the other is neutral.We can conclude that

A uniform linear charge of 2.0 nC/m is distributed along the x axis from x = 0 to x = 3 m.What is the x component of the electric field at y = 2 m on the y axis?

A long cylindrical conductor (radius = 1.0 mm)carries a charge density of 4.0 pC/m and is inside a coaxial,hollow,cylindrical conductor (inner radius = 3.0 mm,outer radius = 4.0 mm)that has a total charge of -8.0 pC/m.What is the magnitude of the electric field 2.0 mm from the axis of these conductors?

A charge of 8.0 pC is distributed uniformly on a spherical surface (radius = 2.0 cm),and a second charge of -3.0 pC is distributed uniformly on a concentric spherical surface (radius = 4.0 cm).Determine the magnitude of the electric field 5.0 cm from the center of the two surfaces.