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Conceptual questions

Is the object in a conductor or an insulator? Justify your answer.

External field lines entering the object from one end and emerging from another are shown by lines.
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If the electric field lines in the figure above were perpendicular to the object, would it necessarily be a conductor? Explain.

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The discussion of the electric field between two parallel conducting plates, in this module states that edge effects are less important if the plates are close together. What does close mean? That is, is the actual plate separation crucial, or is the ratio of plate separation to plate area crucial?

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Would the self-created electric field at the end of a pointed conductor, such as a lightning rod, remove positive or negative charge from the conductor? Would the same sign charge be removed from a neutral pointed conductor by the application of a similar externally created electric field? (The answers to both questions have implications for charge transfer utilizing points.)

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Why is a golfer with a metal club over her shoulder vulnerable to lightning in an open fairway? Would she be any safer under a tree?

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Can the belt of a Van de Graaff accelerator be a conductor? Explain.

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Are you relatively safe from lightning inside an automobile? Give two reasons.

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Discuss pros and cons of a lightning rod being grounded versus simply being attached to a building.

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Using the symmetry of the arrangement, show that the net Coulomb force on the charge q size 12{q} {} at the center of the square below ( [link] ) is zero if the charges on the four corners are exactly equal.

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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.
Four point charges q a size 12{q rSub { size 8{a} } } {} , q b size 12{q rSub { size 8{b} } } {} , q c size 12{q rSub { size 8{c} } } {} , and q d size 12{q rSub { size 8{d} } } {} lie on the corners of a square and q size 12{q} {} is located at its center.

(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 b size 12{q rSub { size 8{a} } =q rSub { size 8{b} } } {} and q b = q c size 12{q rSub { size 8{b} } =q rSub { size 8{c} } } {}

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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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Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
what is titration
John Reply
what is physics
Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
what is inorganic
emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what's motion
Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
hello friend how are you
Muhammad Reply
fine, how about you?
Mohammed
hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
Who can show me the full solution in this problem?
Reofrir Reply
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Source:  OpenStax, College physics for ap® courses. OpenStax CNX. Nov 04, 2016 Download for free at https://legacy.cnx.org/content/col11844/1.14
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