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A point charge of 6.0 pC is located on the x axis at x = 3.0 m.
Calculate the work done on the point charge by an external force to move the point charge to the origin. ...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157493

$ 1.5 




Two tiny metal spheres A and B of mass mA = 5.00 g and mB = 10.0 g have equal positive charges q = 5.00 pC.
The spheres are connected by a massless nonconducting string of length d = 1.00 m, which is much greater than the radii of the spheres.
(a) What is the electric potential energy of the system?
(b) Suppose you cut the string. At that instant, what is the acceleration of each sphere .
(c) A long time after you cut the string, what is the speed of each sphere?
...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157494

$ 2.0 




A thin, spherical, conducting shell of radius R is mounted on an isolating support and charged to a potential of V.
An electron is then fired from point P at distance r from the center of the shell (r>>R) with initial speed v0 and directly toward the shell's center.
What value of v0 is needed for the electron to just reach the shell before reversing direction? ...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157495

$ 1.0 




Two electrons are fixed 2.0 cm apart. Another electron is shot from infinity and stops midway between the two.
What is its initial speed ? ...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157496

$ 1.0 




Two charged, parallel, flat conducting surfaces are spaced d = 1.00 cm apart and produce a potential difference Delta_V = 625 V between them.
An electron is projected from one surface directly toward the second.
What is the initial speed of the electron if it stops just at the second surface? ...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157497

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An electron is projected with an initial speed of 3.2 x 10^5 m/s directly toward a proton that is fixed in place.
If the electron is initially a great distance from the proton, at what distance from the proton is the speed of the electron instantaneously equal to twice the initial value?
...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157498

$ 1.0 




An empty hollow metal sphere has a potential of +400 V with respect to ground (defined to be at V = 0) and has a charge of 5.0 x 10^(9) C.
Find the electric potential at the center of the sphere. ...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157499

$ 0 




What is the excess charge on a conducting sphere of radius r = 0.15 m if the potential of the sphere is 1500 V and V = 0 at infinity?
...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157500

$ 1.0 




Consider two widely separated conducting spheres, 1 and 2, the second having twice the diameter of the first. The smaller sphere initially has a positive charge q , and the larger one is initially uncharged. You now connect the spheres with a long thin wire.
(a)How are the final potentials V1 and V2 of the spheres related?
(b)What are the final charges q1 and q2 on the spheres, in terms of q?
(c) What is the ratio of the final surface charge density of sphere 1 to that of sphere 2?
...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157501

$ 1.5 




Two metal spheres, each of radius 3.0 cm, have a centertocenter separation of 2.0 m. One has a charge of +1.0 x 10^(8) C; the other has a charge of 3.0 x 10^(8) C. Assume that the sepa¬ration is large enough relative to the size of the spheres to permit us to consider the charge on each to be uniformly distributed (the spheres do not affect each other). With V = 0 at infinity, calculate
(a)the potential at the point halfway between their centers and
(b)the potential of each sphere .
...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157502

$ 2.0 




A charged metal sphere of radius 15 cm has a net charge of 3.0 x 10^(8) C.
(a) What is the electric field at the sphere's surface?
(b) If V = 0 at infinity, what is the electric potential at the sphere's surface?
(c) At what distance from the sphere's surface has the electric potential decreased by 500 V? ...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157503

$ 1.5 




(a) If Earth had a net surface charge density of 1.0 electron per square meter (a very artificial assumption), what would its potential be?
(Set V = 0 at infinity.)
(b) What would be the electric field due to Earth just outside its surface?
...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157504

$ 1.0 




Two thin, isolated, concentric conducting spheres of radii R1 and R2 (with R1 < R2) have charges q1 and q2.
With V = 0 at infinity, derive expressions for E(r) and V(r), where r is distance from the center of the spheres.
Plot E(r) and V(r) from r = 0 to r = 4.0 m for R1 = 0.50 m, R2 = 1.0 m, q1 = +2.0 microC, and q2 = +1.0 microC. ...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157505

$ 2.0 




I. The chocolate crumb mystery. Explosions ignited by electro¬static discharges (sparks) constitute a serious danger in facilities handling grain or powder. Such an explosion occurred in chocolate crumb powder at a biscuit factory in the 1970s. At the factory , workers usually emptied newly delivered sacks of the powder into a loading bin, from which it was blown through grounded PVC pipes to a silo for storage. Somewhere along this route, two conditions for an explosion were met:
(1) The magnitude of an electric field became 3.0 x 10^6 N/C or greater, so that electric breakdown and thus sparking could occur.
(2) The energy of a spark was 150 mJ or greater so that it could ignite the powder explosively. Let us check for the first condition in the powder flow through the PVC pipes.
II. Suppose a stream of negatively charged chocolate crumb powder is blown through a cylindrical PVC pipe with radius R = 5.0 cm.
Assume that the powder and its charge are spread uniformly through the pipe with a volume charge density Ro .
(a) Using Gauss" law, find an expression for the magnitude of the density field E in the pipe as a function of the radial distance r from the center of the pipe.
(b) Does the magnitude increase or decrease with r?
(с) Is the electric field E directed radially inward or outward?
(d) Assuming a volume charge density Ro of magnitude 1.1 x 10^(3)C/m^3 (which was typical at the biscuit factory) , find the maximum magnitude of the electric field and determine where that maximum field occurs,
(e) Could sparking occur, and if so. where?
...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157506

$ 2.0 




26.1 Deﬁnition of Capacitance
26.2 Calculating Capacitance
26.3 Combinations of Capacitors
26.4 Energy Stored in a Charged Capacitor
26.5 Capacitors with Dielectrics
26.6 (Optional) Electric Dipole in an Electric Field
26.7 (Optional) An Atomic Description of Dielectrics ...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157507

$ 0 




The two metal objects in Fig. have net charges of +70 pC and 70 pC, which result in a 20 V potential difference between them,
(a) What is the capacitance of the system?
(b) If the charges are changed to +200 pC and 200 pC, what does the capaci¬tance become?
(c) What does the potential difference become? ...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157586

$ 1.0 




The capacitor in Fig. has a capacitance of 25 microF and is initially uncharged. The battery provides a potential difference of 120 V.
After switch S is closed, how much charge will pass through it?
...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157588

$ 1.0 




A parallelplate capacitor has circular plates of 8.2 cm radius and 1.3 mm separation,
(a) Calculate the capacitance,
(b) What charge will appear on the plates if a potential difference of 120 V is applied? ...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157589

$ 1.0 




You have two flat metal plates, each of area 1.00 m^2, with which to construct a parallelplate capacitor.
If the capacitance of the device is to be 1.00 F, what must be the separation between the plates?
Could this capacitor actually be constructed? ...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157590

$ 1.0 




A spherical drop of mercury of radius R has a capacitance given by C = 4PiEpsilonR. If two such drops combine to form a single larger drop, what is its capacitance? ...MORE
Subject: Physics  Topic: Electricity and Magnetism  ID: 157591

$ 1.0 

