Deck 17: Current and Resistance Electric Current: Part A

Question 1

Two point charges are 4 cm apart.They are moved to a new separation of 8 cm.By what factor does the resulting mutual force between them change?

A) 1/4
B) 2
C) 1/2
D) 4

Answer 1

1/4

Question 2

Two identical spheres each carry a charge of −40.0 µC.The spheres are separated by a distance of 2.00 m.What is the electric force between the spheres? (k_e = 8.99 × 10⁹ N·m²/C²)

A) 43.2 N (attractive)
B) 14.4 N (repulsive)
C) 3.60 N (repulsive)
D) 7.19 N (attractive)

Answer 2

3.60 N (repulsive)

Question 3

A proton initially moves left to right long the x axis at a speed of 2.00 × 10³ m/s.It moves into an electric field,which points in the negative x direction,and travels a distance of 0.300 m before coming to rest.If the proton's mass and charge are 1.67 × 10−²⁷ kg and 1.60 × 10−¹⁹ C,respectively,what is the magnitude of the electric field?

A) 13.9 N/C
B) 0.0696 N/C
C) 28.3 N/C
D) 0.104 N/C

Answer 3

0.0696 N/C

Question 4

If two 1.0-C charges have a force between them of 1.0 N,what is their separation?

A) 8.1 × 10¹⁹ m
B) 1.0 m
C) 9.5 × 10⁴ m
D) 9.0 × 10¹⁰ m

Question 5

The charge per unit length on an insulator is 6.2 μC/m.On a 2.0-m length of this material,what is the difference in the number of electrons and the number of protons?

A) There are 7.8 × 10¹³ more electrons than protons.
B) There are 7.8 × 10¹³ more protons than electrons.
C) There are 3.9 × 10¹³ more protons than electrons.
D) There are 3.9 × 10¹³ more electrons than protons.

Question 6

Two point charges,one q and the other -q,form a dipole separated by a distance 2L.A third charge Q is placed midway between these two charges.If the only charge that is negative is -q,what is the force on Q?

A)
toward -q
B)
toward q
C)
toward -​q
D)
toward q

Question 7

An electron is sent at high speed toward a gold nucleus (charge +79e).What is the electrical force acting on the electron when it is 3.0 × 10−¹³ m away from the gold nucleus? (e = 1.6 × 10−¹⁹ C,k_e = 8.99 × 10⁹ N·m²/C²)

A) 2.1 × 10−⁶ N
B) 2.0 × 10−⁴ N
C) 0.20 N
D) 20 N

Question 8

If the distance between two point charges is quadrupled,the mutual force between them will be changed by what factor?

A) 8
B) 4
C) 1/16
D) 1/4

Question 9

Two point charges,separated by 15 cm,have charge values of +2.0 µC and −4.0 µC,respectively.What is the value of the mutual force between them? (k_e = 8.99 × 10⁹ N⋅m²/C²)

A) 8.0 × 10−¹² N
B) 3.6 × 10−⁸ N
C) 320 N
D) 3.2 N

Question 10

Two point charges are separated by 10.0 cm and have charges of +1.00 µC and −1.00 µC,respectively.What is the electric field at a point midway between the two charges? (k_e = 8.99 × 10⁹ N·m²/C²)

A) 14.4 × 10⁶ N/C
B) zero
C) 28.8 × 10⁶ N/C
D) 7.19 × 10⁶ N/C

Question 11

Two point charges are placed along a horizontal axis with the following values and positions: +3.0 µC at x = 0 cm and −6.0 µC at x = 20 cm.At what point along the x axis is the electric field zero?

A) 8.0 cm
B) −48 cm
C) −38 cm
D) −69 cm

Question 12

Charges of 4.0 µC and −6.0 µC are placed at two corners of an equilateral triangle with sides of 0.20 m.At the third corner,what is the electric field magnitude created by these two charges? (k_e = 8.99 × 10⁹ N·m²/C²)

A) 3.1 × 10⁶ N/C
B) 1.2 × 10⁶ N/C
C) 4.8 × 10⁶ N/C
D) 4.5 × 10⁶ N/C

Question 13

An electron with a charge value of 1.6 × 10−¹⁹ C is moving in the presence of an electric field of 300 N/C.What force does the electron experience?

A) 2.3 × 10−²² N
B) 4.8 × 10−¹⁷ N
C) 6.4 × 10−¹⁷ N
D) 1.9 × 10−²¹ N

Question 14

Object A has a charge q on it,object B has a charge q on it,and object C has a charge 2q on it.These charges are arranged,one each,at the vertices of an equilateral triangle.Which charge has the greatest magnitude electric force on it?

A) A
B) C
C) B
D) All have equal magnitude forces on them.

Question 15

A metallic object holds a charge of −2.9 × 10−⁵ C.What total number of electrons does this represent? (e = 1.6 × 10−¹⁹ C is the magnitude of the electronic charge. )

A) 1.8 × 10¹⁴
B) 2.4 × 10¹³
C) 6.1 × 10¹³
D) 4.2 × 10¹⁴

Question 16

If the size of the charge value is tripled for one of two point charges maintained at a constant separation,the mutual force between them will be changed by what factor?

A) 3.0
B) 1/9
C) 9.0
D) 0.33

Question 17

An electron with a speed of 2.0 × 10⁶ m/s moves into a uniform electric field of 325 N/C that is parallel to the electron's motion.How long does it take to bring the electron to rest? (me = 9.11 × 10−³¹ kg,e = 1.6 × 10−¹⁹ C)

A) 3.5 × 10−⁸ s
B) 2.3 × 10−⁶ s
C) 2.3 × 10−⁸ s
D) 1.2 × 10−⁷ s

Question 18

Two point charges,one ​q and the other -q,form a dipole separated by a distance d.A third charge Q is placed midway between these two charges.If the distance between q and -q is then doubled with the Q staying midway between the other two,what happens to the force on Q?

A) It halves.
B) It reduces by a factor of 8.
C) It stays the same.
D) It quarters.

Question 19

About how many electrons are in 0.3 gram of water (H₂O)?

A) 10²³
B) 10²¹
C) 10²⁵
D) 10¹⁹

Question 20

Two point charges each have a value of 30.0 mC and are separated by a distance of 3.00 cm.What is the electric field midway between the two charges? (k_e = 8.99 × 10⁹ N·m²/C²)

A) 40.5 × 10⁷ N/C
B) 20.3 × 10⁷ N/C
C) zero
D) 10.1 × 10⁷ N/C

Question 21

A spherical volume of space has an electric field of intensity 170 N/C directed radially outward from it surface of radius 0.600 m.What is the net charge enclosed within this surface?

A) -6.8 nC
B) -4.0 nC
C) 4.0 nC
D) 6.8 nC

Question 22

A ping-pong ball covered with a conducting graphite coating has a mass of 2.5 × 10−³ kg and a charge of 4.0 µC.What electric field directed upward will exactly balance the weight of the ball? (g = 9.8 m/s²)

A) 6.1 × 10³ N/C
B) 2.0 × 10−⁷ N/C
C) 5.1 × 10⁶ N/C
D) 1.2 × 10⁴ N/C

Question 23

A Van de Graaff generator has a spherical dome of radius 12 cm.Operating in dry air,where "atmospheric breakdown" is at E_max = 3.0 × 10⁶ N/C,what is the maximum charge that can be held on the dome? (k_e = 8.99 × 10⁹ N⋅m²/C²)

A) 4.8 × 10−⁶ C
B) 1.3 × 10−⁵ C
C) 2.7 × 10−⁵ C
D) 3.3 × 10−⁶ C

Question 24

Electrons in a particle beam each have a kinetic energy of 3.2 × 10−¹⁷ J.What is the magnitude of the electric field that will stop these electrons in a distance of 0.05 m? (e = 1.6 × 10−¹⁹ C)

A) 2000 N/C
B) 4000 N/C
C) 200 N/C
D) 1000 N/C

Question 25

Five equal negative charges are uniformly spaced in a semicircular arc of radius r₀ with its center at the origin.The charges positions in polar coordinates are given by (r₀,θ​_i),where the values of θ​_i are 0°,45°,90°,135°,and 180°.At the position (x,y)= (r₀,-r₀)in the 4th quadrant,which statement best describes the direction of the resulting electric field?

A) The direction is that of a 4th quadrant angle.
B) The direction is that of a 3rd quadrant angle.
C) The direction is that of a 1st quadrant angle.
D) The direction is that of a 2nd quadrant angle.

Question 26

A conducting spherical shell of inner radius
And outer radius
Has a charge Q on it.The flux through a concentric spherical surface of radius
Is
)An additional charge,also Q,is then added to the sphere.What is the change in flux through a concentric spherical surface of radius
When the additional charge is placed on the conducting shell?

A)

B)

C)

D) 0

Question 27

We have an initially uncharged hollow metallic sphere with radius of 5.0 cm.I place a small object with a charge of +40 µC at the center of the sphere through a hole in the surface.Find the electric field present at a point 10 cm from the sphere's center.(k_e = 8.99 × 10⁹ N⋅m²/C²)

A) 9.0 × 10⁶ N/C
B) 1.1 × 10⁶ N/C
C) 2.3 × 10⁶ N/C
D) 36 × 10⁶ N/C

Question 28

A proton moving at 6.0 × 10⁴ m/s is projected at an angle of 30° above a horizontal plane.If an electric field of 400 N/C is acting down,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)

A) 7.8 × 10−⁶ s
B) 1.6 × 10−⁶ s
C) 7.8 × 10−⁷ s
D) 3.9 × 10−⁶ s

Question 29

A conducting spherical shell of inner radius r₁ and outer radius r₂ has a charge Q on it.An additional charge,also Q,is then added to the sphere.What is the resulting charge per unit area on the outer surface of the sphere?

A)

B) No answer given is correct.
C)

D)

Question 30

A ring of charge of radius r₀ lies in the x-y plane with its center at the origin.The charge counterclockwise from θ = 0º to θ = 180º is uniformly distributed with the total charge equaling Q.The charge counterclockwise from θ = 180º to θ = 360º is uniformly distributed with the total charge for this half of the ring equaling -Q.What is the direction of the electric field on the z-axis at the position (x,y,z)= (0,0,​r₀)?

A) It is in the +y direction.
B) It is in the -z direction.
C) It is in the -​y direction.
D) It has no direction since
there.

Question 31

We have a hollow metallic sphere with charge +5.0 µC and radius 5.0 cm.We insert a −10 µC charge at the center of the sphere through a hole in the surface.What charge now rests on the outer surface of the sphere?

A) +10 µC
B) +5 µC
C) −5 µC
D) +15 µC

Question 32

If a negative charge is placed inside a hollow isolated conductor that is originally neutral and the charge does not touch that conductor at any time:

A) both the inner and outer surfaces will become negative.
B) both the inner and outer surfaces will remain neutral.
C) the outside surface of the conductor will become positively charged.
D) the inside surface of the conductor will become positively charged.

Question 33

A charge Q accumulates on the hollow metallic dome,of radius R,of a Van de Graaff generator.A probe measures the electric field strength at various points outside the sphere surface.If the probe is initially at a distance 3R from the sphere's center and then is moved to 5R,by what factor will the electric field reading change?

A) 3/5
B) (5/3)²
C) 5/3
D) (3/5)²

Question 34

Q₁ has 27 electric field lines radiating outward and Q₂ has 11 field lines converging inward.What is the ratio Q₁/Q₂?

A) 27/11
B)

C) −11/27
D) −27/11

Question 35

The electric field in a cathode ray tube is supposed to accelerate electrons from 0 to 1.60 × 10⁷ m/s in a distance of 4.00 cm.What electric field is required? (m_e = 9.11 × 10−³¹ kg and e = 1.60 × 10−¹⁹ C)

A) 18,200 N/C
B) 9110 N/C
C) 36,400 N/C
D) 72,800 N/C

Question 36

In x-ray machines,electrons are subjected to electric fields as great as 4.0 × 10⁵ N/C.Find an electron's acceleration in this field.(m_e = 9.11 × 10−³¹ kg,e = 1.6 × 10−¹⁹ C)

A) 1.1 × 10¹⁷ m/s²
B) 7.0 × 10¹⁶ m/s²
C) 3.6 × 10⁸ m/s²
D) 4.6 × 10¹⁰ m/s²

Question 37

A charge Q accumulates on the hollow metallic dome,of radius R,of a Van de Graaff generator.A probe measures the electric field strength at various points outside the sphere's surface.By what factor will the electric field value at the 2R distance be changed if the charge value were increased to (5/3)Q?

A) 3/5
B) (5/3)²
C) 5/3
D) (3/5)²