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(a) Using the symmetry of the arrangement, show that the electric field at the center of the square in [link] is zero if the charges on the four corners are exactly equal. (b) Show that this is also true for any combination of charges in which q a = q d size 12{q rSub { size 8{a} } =q rSub { size 8{d} } } {} and q b = q c size 12{q rSub { size 8{b} } =q rSub { size 8{z} } } {}

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(a) What is the direction of the total Coulomb force on q size 12{q} {} in [link] if q size 12{q} {} is negative, q a = q c size 12{q rSub { size 8{a} } =q rSub { size 8{c} } } {} and both are negative, and q b = q c size 12{q rSub { size 8{b} } =q rSub { size 8{c} } } {} and both are positive? (b) What is the direction of the electric field at the center of the square in this situation?

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Considering [link] , suppose that q a = q d size 12{q rSub { size 8{a} } =q rSub { size 8{d} } } {} and q b = q c size 12{q rSub { size 8{b} } =q rSub { size 8{c} } } {} . First show that q size 12{q} {} is in static equilibrium. (You may neglect the gravitational force.) Then discuss whether the equilibrium is stable or unstable, noting that this may depend on the signs of the charges and the direction of displacement of q size 12{q} {} from the center of the square.

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If q a = 0 size 12{q rSub { size 8{a} } =0} {} in [link] , under what conditions will there be no net Coulomb force on q size 12{q} {} ?

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In regions of low humidity, one develops a special “grip” when opening car doors, or touching metal door knobs. This involves placing as much of the hand on the device as possible, not just the ends of one’s fingers. Discuss the induced charge and explain why this is done.

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Tollbooth stations on roadways and bridges usually have a piece of wire stuck in the pavement before them that will touch a car as it approaches. Why is this done?

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Suppose a woman carries an excess charge. To maintain her charged status can she be standing on ground wearing just any pair of shoes? How would you discharge her? What are the consequences if she simply walks away?

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Problems&Exercises

Sketch the electric field lines in the vicinity of the conductor in [link] given the field was originally uniform and parallel to the object’s long axis. Is the resulting field small near the long side of the object?

A oblong-shaped conductor.
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Sketch the electric field lines in the vicinity of the conductor in [link] given the field was originally uniform and parallel to the object’s long axis. Is the resulting field small near the long side of the object?

A oblong-shaped conductor.
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Sketch the electric field between the two conducting plates shown in [link] , given the top plate is positive and an equal amount of negative charge is on the bottom plate. Be certain to indicate the distribution of charge on the plates.

Two plates are shown; one is in horizontal direction and other is above the first plate with some inclination.
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Sketch the electric field lines in the vicinity of the charged insulator in [link] noting its nonuniform charge distribution.

A positively charged rod with a concentration of positive charges near the top and a few in the middle.
A charged insulating rod such as might be used in a classroom demonstration.
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What is the force on the charge located at x = 8.00 cm in [link] (a) given that q = 1 . 00 μC size 12{q=1 "." "00""μC"} {} ?

Three point charges are shown on the scaling line. First charge plus q is at three point zero, second charge minus two q is at eight point zero, and third charge plus q is eleven point zero centimeters along the x axis. Four charges are placed on a scaling line. First is minus two q at one point zero, second is plus q at five point zero, third is plus three q is at eight point zero, and fourth is minus q placed at fourteen point zero centimeter along the x axis.
(a) Point charges located at 3.00, 8.00, and 11.0 cm along the x -axis. (b) Point charges located at 1.00, 5.00, 8.00, and 14.0 cm along the x -axis.
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(a) Find the total electric field at x = 1.00 cm in [link] (b) given that q = 5.00 nC . (b) Find the total electric field at x = 11.00 cm in [link] (b). (c) If the charges are allowed to move and eventually be brought to rest by friction, what will the final charge configuration be? (That is, will there be a single charge, double charge, etc., and what will its value(s) be?)

(a) E x = 1.00 cm = size 12{E rSub { size 8{x=1 "." "00" ital "cm"} } = - infinity } {}

(b) 2 . 12 × 10 5 N/C size 12{ {underline {2 "." "12" times "10" rSup { size 8{5} } " N/C" {underline {}} }} } {}

(c) one charge of + q

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(a) Find the electric field at x = 5.00 cm in [link] (a), given that q = 1.00 μC size 12{q=1 "." "00""μC"} {} . (b) At what position between 3.00 and 8.00 cm is the total electric field the same as that for –2 q alone? (c) Can the electric field be zero anywhere between 0.00 and 8.00 cm? (d) At very large positive or negative values of x , the electric field approaches zero in both (a) and (b). In which does it most rapidly approach zero and why? (e) At what position to the right of 11.0 cm is the total electric field zero, other than at infinity? (Hint: A graphing calculator can yield considerable insight in this problem.)

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(a) Find the total Coulomb force on a charge of 2.00 nC located at x = 4.00 cm in [link] (b), given that q = 1.00 μC size 12{q=1 "." "00""μC"} {} . (b) Find the x -position at which the electric field is zero in [link] (b).

(a) 0.252 N to the left

(b) x = 6.07 cm

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Using the symmetry of the arrangement, determine the direction of the force on q size 12{q} {} in the figure below, given that q a = q b =+ 7 . 50 μC size 12{q rSub { size 8{a} } =q rSub { size 8{b} } "=+"7 "." "50""μC"} {} and q c = q d = 7 . 50 μC size 12{q rSub { size 8{c} } =q rSub { size 8{d} } = - 7 "." "50""μC"} {} . (b) Calculate the magnitude of the force on the charge q size 12{q} {} , given that the square is 10.0 cm on a side and q = 2 . 00 μC size 12{q=2 "." "00""μC"} {} .

Four point charges, one is q a, second is q b, third is q c, and fourth is q d, lie on the corners of a square. q is located at its center.
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(a) Using the symmetry of the arrangement, determine the direction of the electric field at the center of the square in [link] , given that q a = q b = 1 . 00 μC size 12{q rSub { size 8{a} } =q rSub { size 8{b} } = - 1 "." "00""μC"} {} and q c = q d =+ 1 . 00 μC size 12{q rSub { size 8{c} } =q rSub { size 8{d} } "=+"1 "." "00""μC"} {} . (b) Calculate the magnitude of the electric field at the location of q size 12{q} {} , given that the square is 5.00 cm on a side.

(a)The electric field at the center of the square will be straight up, since q a size 12{q rSub { size 8{a} } } {} and q b size 12{q rSub { size 8{b} } } {} are positive and q c size 12{q rSub { size 8{c} } } {} and q d size 12{q rSub { size 8{d} } } {} are negative and all have the same magnitude.

(b) 2 . 04 × 10 7 N/C ( upward ) size 12{ {underline {2 "." "04" times "10" rSup { size 8{7} } " N/C" \( "upward" \) }} } {}

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Find the electric field at the location of q a size 12{q rSub { size 8{a} } } {} in [link] given that q b = q c = q d =+ 2 . 00 nC size 12{q rSub { size 8{b} } =q rSub { size 8{c} } =q rSub { size 8{d} } "=+"2 "." "00""nC"} {} , q = 1 . 00 nC size 12{q= - 1 "." "00""nC"} {} , and the square is 20.0 cm on a side.

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Find the total Coulomb force on the charge q in [link] , given that q = 1 . 00 μC size 12{q=1 "." "00""μC"} {} , q a = 2 . 00 μC size 12{q rSub { size 8{a} } =2 "." "00""μC"} {} , q b = 3 . 00 μC size 12{q rSub { size 8{b} } = - 3 "." "00""μC"} {} , q c = 4 . 00 μC size 12{q rSub { size 8{c} } = - 4 "." "00""μC"} {} , and q d =+ 1 . 00 μC size 12{q rSub { size 8{d} } "=+"1 "." "00""μC"} {} . The square is 50.0 cm on a side.

0 . 102 N , size 12{0 "." "102"" N",} {} in the y size 12{ - y ital } {} {} {} {} direction

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(a) Find the electric field at the location of q a in [link] , given that q b = +10.00 μ C and q c = –5.00 μ C . (b) What is the force on q a , given that q a = +1.50 nC ?

Three point charges located at the corners of an equilateral triangle.
Point charges located at the corners of an equilateral triangle 25.0 cm on a side.
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(a) Find the electric field at the center of the triangular configuration of charges in [link] , given that q a =+ 2 . 50 nC size 12{q rSub { size 8{a} } "=+"2 "." "50""nC"} {} , q b = 8 . 00 nC size 12{q rSub { size 8{b} } = - 8 "." "00""nC"} {} , and q c =+ 1 . 50 nC size 12{q rSub { size 8{c} } "=+"1 "." "50""nC"} {} . (b) Is there any combination of charges, other than q a = q b = q c size 12{q rSub { size 8{a} } =q rSub { size 8{b} } =q rSub { size 8{c} } } {} , that will produce a zero strength electric field at the center of the triangular configuration?

(a) E = 4.36 × 10 3 N/C , 35.0º , below the horizontal.

(b) No

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Questions & Answers

what is motion
Ali Reply
When a body changes its position with respect to its surroundings then it is said to be in motion
Jon
it is a change in position, direction, shape and arrangement of a body or an object which is initially at rest
Abolarin
Pls guys am having problem on these topics: latent heat of fusion, specific heat capacity and the sub topics under them.Pls who can help?
hamidat Reply
Thanks George,I appreciate.
hamidat
this will lead you rightly of the formula to use
Abolarin
Most especially it is the calculatory aspects that is giving me issue, but with these new strength that you guys have given me,I will put in my best to understand it again.
hamidat
you can bring up a question and let's see what we can do to it
Abolarin
I also have a problem with the calculation sincerely
Sulaimon
the distance between two suasive crests of water wave traveling of 3.6ms1 is 0.45m calculate the frequency of the wave
Idris Reply
v=f×lemda where the velocity is given and lends also given so simply u can calculate the frequency
Abdul
You are right my brother, make frequency the subject of formula and equate the values of velocity and lamda into the equation, that all.
hamidat
lExplain what happens to the energy carried by light that it is dimmed by passing it through two crossed polarizing filters.
Christoper Reply
When light is reflected at Brewster's angle from a smooth surface, it is 100% polarizedparallel to the surface. Part of the light will be refracted into the surface.
Ekram
What is specific heat capacity?
hamidat Reply
Specific heat capacity is the amount of heat required to raise the temperature of one (Kg) of a substance through one Kelvin
Paluutar
formula for measuring Joules
Rowshan Reply
I don't understand, do you mean the S.I unit of work and energy?
hamidat
what are the effects of electric current
ADAMS Reply
What limits the Magnification of an optical instrument?
Naeem Reply
Lithography is 2 micron
Venkateshwarlu
what is expression for energy possessed by water ripple
Prabesh Reply
what is hydrolic press
Mark Reply
An hydraulic press is a type of machine that is operated by different pressure of water on pistons.
hamidat
what is dimensional unite of mah
Patrock Reply
i want jamb related question on this asap🙏
sharon Reply
What is Boyles law
Pascal Reply
it can simple defined as constant temperature
Muhammad
Boyles law states that the volume of a fixed amount of a gas is inversely proportional to the pressure acting on in provided that the temperature is constant.that is V=k(1/p) or V=k/p
FADILAT
what is motion
Mua Reply
getting notifications for a dictionary word, smh
Anderson
what is escape velocity
Shuaibu Reply
the minimum thrust that an object must have in oder yo escape the gravitational pull
Joshua
what is a dimer
Mua
what is a atom
ADAMS
Practice Key Terms 6

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Source:  OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
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