Physics final

Two tiny beads are 25 cm apart with no other charges or fields present. Bead A carries 10 µC of charge and bead B carries 1 µC. Which one of the following statements is true about the magnitudes of the electric forces on these beads?

C. The force on A is exactly equal to the force on B. Correct

As you walk away from a plane mirror on a wall, the height of your image

C. is always the same size.

As a proton moves in the direction the electric field lines

D. it is moving from high potential to low potential and losing electric potential energy. Correct

An electron is initially moving to the right when it enters a uniform electric field directed upwards, as shown in the figure. Which trajectory (X, Y, Z, or W) will the electron follow in the field?

D. trajectory Z

The focal length of a concave mirror has a magnitude of 20 cm. What is its radius of curvature?

E. 40 cm

Two 10¢ coins (dimes) carrying identical charges are lying 2.5 m apart on a table. If each of these coins experiences an electrostatic force of magnitude 2.0 N due to the other coin, how large is the charge on each coin? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2)

E. 52 μC Correct

Which of following statements about the image formed by a single converging lens are true? (There could be more than one correct choice.)

E. None of the above choices are correct.

A convex lens has focal length f. If an object is placed at a distance beyond 2f from the lens on the principal axis, the image is located at a distance from the lens

E. between f and 2f.

You may have seen ambulances on the street with the letters of the word AMBULANCE written on the front of them, in such a way as to appear correctly when viewed in your car's rear-view mirror. (See the figure.) How do the letters appear when you look directly at the ambulance (not through the mirror)?

E. e

Two stationary point charges q1 and q2 are shown in the figure along with a sketch of some field lines representing the electric field produced by them. What can you deduce from the sketch?

E. q1 is negative and q2 is positive; the magnitude of q1 is less than the magnitude of q2. Correct

A convex lens has focal length f. If an object is placed at a distance between f and 2f from the lens on the principal axis, the image is located at a distance from the lens

E. that is greater than 2f.

Three equal positive point charges +q are placed at the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the center of the square?

A. A Correct

Which one of the arrows shown in the figure best represents the direction of the electric field between the two uniformly charged metal plates?

A. A Correct

The image formed in a plane mirror is

A. at the same distance behind the mirror as the object is in front of the mirror.

Three equal charges +Q are at three of the corners of a square of side d. A fourth charge +Q of equal magnitude is at the center of the square as shown in the figure Which one of the arrows shown represents the net force acting on the charge at the center of the square?

B. B

The electron-volt is a unit of

B. energy. Correct

Four charged particles (two having a charge +Q and two having a charge -Q) are arranged in the xy-plane as shown in the figure. The charges are all equidistant from the origin. The amount of work required to move a positively charged particle from point P to point O (both of which are on the z-axis) is

B. zero.

Is it possible to see a virtual image?

Yes because the rays that appear to come from a virtual image can be focused by the eye just like those from an object.

The critical angle for a beam of light passing from water into air is 48.8°. This means that all light rays with an angle of incidence in the water that is greater than 48.8° will be

totally reflected.

If you stand in front of a convex mirror, at the same distance from it as its focal length,

you will see your image and you will appear smaller than you.

Two 5.0-µC point charges are 12 cm apart. What is the electric potential (relative to infinity) of this combination at the point where the electric field due to these charges is zero? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2)

B. 1.5 MV

How much kinetic energy does a proton gain if it is accelerated, with no friction, through a potential difference of 1.00 V? The proton is 1836 times heavier than an electron, and e = 1.60 × 10-19 C.

B. 1.60 × 10-19 eV Incorrect

The potential (relative to infinity) at the midpoint of a square is 3.0 V when a point charge of +Q is located at one of the corners of the square. What is the potential (relative to infinity) at the center when each of the other corners is also contains a point charge of +Q?

B. 12 V Correct

If the index of refraction of a material is 2, this means that light travels

B. 2 times as fast in vacuum as it does in the material.

As shown in the figure, three charges are at corners of a rectangle. The charge in the bottom right corner is Q = - 90 nC, and all the other quantities are accurate to two significant figures. What is the magnitude of the net electrical force on Q due to the other two charges? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2)

B. 3.8 × 10-2 N Correct

Two electrons are apart at closest approach. What is the magnitude of the maximum electric force that they exert on each other? (e = 1.60 × 10-19 C, k = 1/4πε0 = 9.0 109 N ∙ m2/C2)

B. 5.8 × 10-25 N Correct

Which statements about images are correct? (There could be more than one correct choice.)

B. A virtual image cannot be formed on a screen.

Three equal negative point charges -q are placed at three of the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the vacant corner of the square?

B. B Correct

Three equal-magnitude point charges of varying signs are placed at three of the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the vacant corner of the square?

B. B Correct

Two point charges, Q1 and Q2, are separated by a distance R. If the magnitudes of both charges are halved and their separation is also halved, what happens to the electrical force that each charge exerts on the other one?

B. It remains the same.

If a spherical convex mirror has a radius of curvature R, the magnitude of its focal length is

B. R/2.

A hydrogen nucleus, which has a charge +e, is situated to the left of a carbon nucleus, which has a charge +6e. Which statement is true?

B. The electrical force experienced by the hydrogen nucleus is to the left, and the magnitude is equal to the force exerted on the carbon nucleus.

Sometimes when you look into a curved mirror you see a magnified image (a great big you) and sometimes you see a diminished image (a little you). If you look at the bottom (convex) side of a shiny spoon, what will you see?

B. You will see a little you, right side up.

If an object is placed at the center of curvature of concave mirror, the image formed by the mirror is located

B. at the center of curvature.

Which of the following terms describe lenses that are thicker at the center than at the edges? (There could be more than one correct choice.)

B. converging lenses Correct D. convex lenses Correct

Single concave spherical mirrors produce images that

B. could be smaller than, larger than, or the same size as the actual object, depending on the placement of the object.

The index of refraction of a type of glass is 1.50, and the index of refraction of water is 1.33. If light enters water from this glass, the angle of refraction will be

B. greater than the angle of incidence.

A convex lens has focal length f. If an object is placed at a distance of 2f from the lens on the principal axis, the image is located at a distance from the lens

B. of 2f.

Four charged particles (two having a charge +Q and two having a charge -Q) are arranged in the xy-plane, as shown in the figure. These particles are all equidistant from the origin. The electric potential (relative to infinity) at point P on the z-axis due to these particles, is

B. zero.

A +5.0-μC point charge is placed at the 0 cm mark of a meter stick and a -4.0-μC charge is placed at the 50 cm mark. What is the net electric field at the 30 cm mark? (k = 1/4πε0 = 8.99 × 109 N ∙ m2/C2)

C. 1.4 × 106 N/C Correct

A small charged plastic ball is vertically above another charged small ball in a frictionless test tube as shown in the figure. The balls are in equilibrium a distance d apart. If the charge on each ball is doubled, the equilibrium distance between the balls in the test tube would become

C. 2d.

The force of attraction that a -40.0 μC point charge exerts on a +108 μC point charge has magnitude 4.00 N. How far apart are these two charges? (k = 1/4πε0 = 8.99 × 109 N ∙ m2/C2)

C. 3.12 m Correct

A +5.00-μC point charge is placed at the 0.0 cm mark of a meter stick and a -4.00-μC point charge is placed at the 50.0 cm mark. At what point on a line through the ends of the meter stick is the electric field equal to zero?

C. 4.7 m from the 0 cm mark Correct

The electric potential at a distance of 4 m from a certain point charge is 200 V relative to infinity. What is the potential (relative to infinity) at a distance of 2 m from the same charge?

C. 400 V Correct

Two tiny particles having charges of +5.00 μC and +7.00 μC are placed along the x-axis. The +5.00-µC particle is at x = 0.00 cm, and the other particle is at x = 100.00 cm. Where on the x-axis must a third charged particle be placed so that it does not experience any net electrostatic force due to the other two particles?

C. 45.8 cm Correct

A proton is placed in an electric field of intensity 800 N/C. What are the magnitude and direction of the acceleration of the proton due to this field? (e = 1.60 × 10-19 C, mproton = 1.67 × 10-27 kg)

C. 7.66 × 1010 m/s2 in the direction of the electric field Correct

The figure shows two tiny 5.0-g spheres suspended from very light 1.0-m-long threads. The spheres repel each other after each one is given the same positive charge and hang at rest when θ = 4.1°. What is the charge on each sphere? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2)

C. 89 nC Correct

Two tiny beads, each of mass 3.2 g, carry equal-magnitude charges. When they are placed 6.4 cm apart and released in outer space, they begin to accelerate toward each other at 538 m/s2. What is the magnitude of the charge on each bead? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2)

C. 890 nC Correct

Three equal negative point charges -q are placed at three of the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the center of the square?

C. C Correct

An electron and a proton are released simultaneously from rest and start moving toward each other due to their electrostatic attraction, with no other forces present. Which of the following statements are true just before they are about to collide? (There could be more than one correct choice.)

C. They are closer to the to the initial position of the proton that to the initial position of the electron.

A lighted candle is placed a short distance from a plane mirror, as shown in the figure. At which location will the image of the flame appear to be located?

C. at C Correct

A hydrogen atom consists of a proton and an electron. If the orbital radius of the electron increases, the electric potential energy of the electron due to the proton

C. increases. Correct

As an electron moves in the direction the electric field lines

C. it is moving from high potential to low potential and gaining electric potential energy.

Light goes from material having a refractive index of n1 into a material with refractive index n2. If the refracted light is bent away from the normal, what can you conclude about the indices of refraction?

C. n1 > n2

If a object is placed between a convex lens and its focal point, the image formed is Select one:

C. virtual and upright

If you stand in front of a convex mirror, at the same distance from it as its radius of curvature,

C. you will see your image and you will appear smaller than you.

Three point charges, -2.00 μC, +4.00 μC, and +6.00 μC, are located along the x-axis as shown in the figure. What is the electric potential (relative to infinity) at point P due to these charges? (k = 1/4πε0 = 8.99 × 109 N ∙ m2/C2)

D. +307 k V

The three point charges shown in the figure form an equilateral triangle with sides 4.9 cm long. What is the electric potential (relative to infinity) at the point indicated with the dot, which is equidistant from all three charges? Assume that the numbers in the figure are all accurate to two significant figures. (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2)

D. 0.00 V

Two equally charged tiny spheres of mass 1.0 g are placed 2.0 cm apart. When released, they begin to accelerate away from each other at What is the magnitude of the charge on each sphere, assuming only that the electric force is present? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2)

D. 140 nC Correct

A sphere with radius 2.0 mm carries a charge. What is the potential difference, between point B, which is from the center of the sphere, and point A, which is from the center of the sphere? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2)

D. 1500 V Correct

As shown in the figure, three charges are at the vertices of an equilateral triangle. The charge Q is 6.7 nC, and all the other quantities are accurate to two significant figures. What is the magnitude of the net electric force on the charge Q due to the other two charges? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2)

D. 2.1 × 10-3 N Correct

If an electron is accelerated from rest through a potential difference of 1500 V, what speed does it reach? (e = 1.60 × 10-19 C , melectron = 9.11 × 10-31 kg)

D. 2.3 × 107 m/s Correct

One point charge +Q is placed at the center of a square, and a second point charge -Q is placed at the upper-left corner of the square. It is observed that an electrostatic force of magnitude 2.0 N acts on the positive charge at the center. Now a third charge -Q is placed at the lower-left corner of the square, as shown in the figure. What is the magnitude of the net force that acts on the center charge now?

D. 2.8 N Correct

An electron is projected with an initial velocity v0 = 8.4 × 107 m/s along the y-axis, which is the centerline between a pair of charged plates, as shown in the figure. The plates are 1.0 m long and are separated by 0.10 m. A uniform electric field of magnitude E in the +x-direction is present between the plates. If the magnitude of the acceleration of the electron is measured to be what is the magnitude of the electric field between the plates? (e = 1.6 × 10-19 C, melectron = 9.11 × 10-31 kg)

D. 51,000 N/C Correct

What is the magnitude of a the vertical electric field that will balance the weight of a plastic sphere of mass that has been charged to -3.0 nC? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2)

D. 6.9 × 106 N/C Correct

Four point charges Q of equal magnitude and sign are arranged on three of the corners of the square of side d as shown in the figure Which one of the arrows shown represents the net force acting on the charge at the upper right hand corner of the square?

D. D

Two point charges, Q1 and Q2, are separated by a distance R. If the magnitudes of both charges are doubled and their separation is also doubled, what happens to the electrical force that each charge exerts on the other one?

D. It remains the same.

Suppose you wanted to start a fire using a mirror to focus sunlight. Which of the following statements is most accurate?

D. It would be best to use a concave mirror, with the object to be ignited positioned halfway between the mirror and its center of curvature

If a spherical concave mirror has a radius of curvature R, its focal length is

D. R/2.

Single convex spherical mirrors produce images that

D. are always smaller than the actual object.

An upright object is 50 cm from a concave mirror of radius 60 cm. The character of the image is

D. real and inverted

A pair of charged conducting plates produces a uniform field of 12,000 N/C, directed to the right, between the plates. The separation of the plates is 40 mm. An electron is projected from plate A, directly toward plate B, with an initial speed of v0 = 2.0 × 107 m/s. What is the speed of the electron as it strikes plate B? (e = 1.6 × 10-19 C, melectron = 9.11 × 10-31 kg)

E. 1.5 × 107 m/s Correct

Two point charges each experience a 1-N electrostatic force when they are 2 cm apart. If they are moved to a new separation of 8 cm, what is the magnitude of the electric force on each of them?

E. 1/16 N Correct

Two identical small charged spheres are a certain distance apart, and each one initially experiences an electrostatic force of magnitude F due to the other. With time, charge gradually diminishes on both spheres by leaking off. When each of the spheres has lost half its initial charge, what will be the magnitude of the electrostatic force on each one?

E. 1/4 F

As a proton moves in a direction perpendicular to the electric field lines

E. both its electric potential and electric potential energy remain constant. Correct

The electric field at point P due to a point charge Q a distance R away from P has magnitude E. In order to double the magnitude of the field at P, you could

E. double the charge to 2Q. Correct

If the magnification of a mirror or lens is negative, it means that

E. the image is inverted.

If a single lens forms a virtual image of an object, then

E. the lens could be either a diverging or a converging lens.

A convex mirror has a focal length of magnitude f. An object is placed in front of this mirror at a point f from the face of the mirror. The image will appear

E. upright and reduced.

Which one of the following sets of characteristics describes the image formed by a plane mirror?

E. virtual and upright

Suppose you place an object in front of a concave mirror. Which of the following statements must be true? (There could be more than one correct choice.)

If you position the object between the mirror and the focal point of the mirror, its image must be upright and virtual.

The focal length of a convex mirror is has a magnitude of 20 cm. What is its radius of curvature?

-40 cm

Which one of the following numbers is the correct magnification produced by a plane mirror?

. 1

Which statement about a single thin lens is correct?

. A diverging lens always produces a virtual upright image.

A beam of light that is parallel to the principal axis strikes a convex mirror. What happens to the reflected beam of light?

. It appears to be coming from the focal point on the other side of the mirror.

A beam of light that is parallel to the principal axis strikes a concave mirror. What happens to the reflected beam of light?

. It passes through the focal point of the mirror.

Starting from very far away, an object is moved closer and closer to a converging lens, eventually reaching the lens. What happens to its image formed by that lens? (There could be more than one correct choice.)

. The image eventually changes from real to virtual. Correct

The image formed by a single concave lens

. is always virtual. Correct

A proton is accelerated from rest through a potential difference V0 and gains a speed v0. If it were accelerated instead through a potential difference of 2V0, what speed would it gain?

. v0 (square root 2) Correct

Light enters air from water. The angle of refraction will be

greater than the angle of incidence.

Three point charges are located on the x-axis at the following positions: Q1 = +2.00 μC is at x = 1.00 m, Q2 = +3.00 μC is at x = 0.00, and Q3 = -5.00 μC is at x = -1.00 m. What is the magnitude of the electric force on Q2? (k = 1/4πε0 = 8.99 × 109 N ∙ m2/C2)

A. 0.189 N Correct

Two tiny particles carrying like charges of the same magnitude are apart. If the electric force on one of them is what is the magnitude of the charge on each of these particles?(k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2)

A. 2.4 × 10-8 C Correct

Two tiny particles having charges +20.0 μC and -8.00 μC are separated by a distance of 20.0 cm. What are the magnitude and direction of electric field midway between these two charges? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2)

A. 25.2 × 106 N/C directed towards the negative charge Correct

Suppose you wanted to hold up an electron against the force of gravity by the attraction of a fixed proton some distance above it. How far above the electron would the proton have to be? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2, e = 1.6 × 10-19 C, mproton = 1.67 × 10-27 kg, melectron = 9.11 × 10-31 kg)

A. 5.1 m Correct

Four point charges of equal magnitudes but with varying signs are arranged on three of the corners and at the center of the square of side d as shown in the figure. Which one of the arrows shown represents the net force acting on the center charge?

A. A

Four point charges of varying magnitude and sign are arranged on the corners of the square of side d as shown in the figure. Which one of the arrows shown represents the net force acting on the point charge with a charge +Q?

A. A Correct

Three equal-magnitude point charges of varying signs are placed at the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the center of the square?

A. A Correct

The figure shows electric field lines arising from two small charged particles P and Q. Consider the following two statements: (i) The charge on P is smaller than the charge on Q. (ii) The electrostatic force on P is smaller than the force on Q. Which of the above statements are true?

A. Only (i) is true. Correct

The figure shows two unequal charges, +q and -Q. Charge -Q has greater magnitude than charge +q. Point X is midway between the charges. In what section of the line will there be a point where the resultant electric field is zero?

A. VW Correct

Which of the following terms describe lenses that are thinner at the center than at the edges? (There could be more than one correct choice.)

A. concave lenses C. diverging lenses

Light enters glass from air. The angle of refraction will be

A. less than the angle of incidence.

A light beam has speed c in vacuum and speed v in a certain plastic. The index of refraction n of this plastic is

A. n = c/v.

A convex lens has focal length f. If an object is located at "infinity" (very far away), the image formed is located at a distance from the lens

A. of f.

An object is placed in front of a convex mirror at a distance larger than twice the magnitude of the focal length of the mirror. The image will appear

A. upright and reduced.

Four tiny charged particles (two having a charge +Q and two having a charge -Q) are distributed on the x- and y-axes as shown in the figure. Each charge is equidistant from the origin. In which direction is the net electric field at the point P on the y-axis?

A. upwards and towards the left

A negative magnification for a mirror means that

the image is inverted, and the mirror is concave.