Physics 236 Worksheet: Chapter 23, Electric Force (1)

1.     An atom consists of 19 protons, 20 neutrons, and 18 electrons. This is a:

a.     neutral atom.

b.      singly charged positive ion.

c.      singly charged negative ion

d.     doubly charged positive ion.

e.     doubly charged negative ion.

2.     Metals are

a.     conductors.

b.      insulators.

c.      semiconductors.

3.     If the distance between two charges is cut in half, the electrical force between them will be

a.     doubled.

b.      cut in half.

c.      multiplied by four.

d.     divided by four.

4.     Q₁ is an electron and Q₂ is a proton. When placed near each other

a.     Q₁ and Q₂ attract each other and Q₁ has the same acceleration as Q₂.

b.      Q₁ and Q₂ attract each other and Q₁ has smaller acceleration than Q₂.

c.      Q₁ and Q₂ attract each other and Q₁ has greater acceleration than Q₂.

d.     Q₁ and Q₂ repel each other and Q₁ has the same acceleration as Q₂

e.     Q₁ and Q₂ repel each other and Q₁ has smaller acceleration than Q₂

f.       Q₁ and Q₂ repel each other and Q₁ has greater acceleration than Q₂

5.     Q₁ = +10 mC and Q₂ = +20 mC. The charges are 0.01 mm apart.

a.     The force on Q₁ is greater than the force on Q₂.

b.      The force on Q₁ is less than the force on Q₂.

c.      The force on each charge is the same.

6.     An electron is released from rest near a proton. Which of the following statements correctly describe the subsequent motion of the electron. There is more than one correct answer.

a.     The electron will move toward the proton with constant velocity.

b.      The electron will move toward the proton with increasing velocity.

c.      The electron will move toward the proton with decreasing velocity.

d.     The electron will move toward the proton with zero acceleration.

e.     The electron will move toward the proton with constant acceleration.

f.       The electron will move toward the proton with increasing acceleration.

g.      The electron will move toward the proton with decreasing acceleration.

h.     The electron will move in a circular orbit around the proton.

7.     A H⁺ ion and a He^- ion are released from rest at points A and B respectively. The point at which they collide will be

a.     midway between A and B.

b.      closer to A than to B.

c.      closer to B than to A.

 

Ans: 1-b, 2-a, 3-c, 4-c. 5-c, 6-b and f, 7-c

 

Physics 236 Worksheet: Chapter 23, Electric Force (2)

1.     Q1, Q2 and Qx are equal positive charges located as shown below.

 

 

a.     The resultant force on Qx is directed to the right.

b.      The resultant force on Qx is directed to the left.

c.      The resultant force on Qx is zero.

2.     Same diagram as #1 but all the charges are negative.

a.     The resultant force on Qx is directed to the right.

b.      The resultant force on Qx is directed to the left.

c.      The resultant force on Qx is zero.

3.     Same diagram as #1 but Q1 and Q2 are equal positive charges and Qx is negative

a.     The resultant force on Qx is directed to the right.

b.      The resultant force on Qx is directed to the left.

c.      The resultant force on Qx is zero.

4.     Same diagram as #1 but Q1 and Q2 are equal negative charges and Qx is positive.

a.     The resultant force on Qx is directed to the right.

b.      The resultant force on Qx is directed to the left.

c.      The resultant force on Qx is zero.

5.     Same diagram as #1 but Q1 and Qx are equal positive charges and Q2 is negative with the same magnitude.

a.     The resultant force on Qx is directed to the right.

b.      The resultant force on Qx is directed to the left.

c.      The resultant force on Qx is zero.

6.     Q1, Q2 and Qx are equal positive charges located as shown below. If Qx is moved slightly to the left, the resultant force on Qx will

a.     increase

b.      decrease

c.      remain the same

 

7.     At which point must a test charge be placed in the diagram below so that the resultant force on it is zero?

a.     Point a

b.      Point b

c.      Point c

d.     Point a if the test charge is positive, c if it is negative.

e.     There is no point between Q and 3Q for which the force on any test charge is zero.

 

Ans: 1-a, 2-a, 3-b, 4-b, 5-a, 6-b, 7-a

 

Physics 236 Worksheet: Chapter 23, Electric Field

 

1.     The electric force acting on a test charge at a point divided by the value of the charge is the

a.     acceleration of the test charge.

b.      electric field created by the test charge.

c.      electric field acting on the test charge.

d.     the energy of the test charge.

2.     The electric field at a distance of 2 mm from a test charge is _  the field at a distance of 4 mm

a.     the same as

b.      twice as strong as

c.      four times as strong as

d.     half as strong as

e.     one fourth as strong as

3.     The electric field midway between two equal positive charges is

a.     twice as strong as the field of one charge alone.

b.      half as strong as the field of one charge alone.

c.      zero.

4.     The electric field midway between equal positive and negative charges is

a.     twice as strong as the field of one charge alone and points toward the negative charge.

b.      twice as strong as the field of one charge alone and points toward the positive charge.

c.      zero.

5.     Which of the following is not true about electric field lines?

a.     Lines begin on positive charge and end on negative.

b.      Lines are close together where the field is strong.

c.      The direction of the electric force on a charge is tangent to the field line.

d.     All these statements are true.

e.     None of these statements are true.

6.     The electric field inside a positively charged conductor in equilibrium

a.     is zero.

b.      points outward.

c.      points inward.

7.     If a negative charge is moving to the north in an electric field which is directed to the north, the charge will

a.     speed up.

b.      slow down.  

c.      be unaffected.

8.     In the figure Q1 is negative and Q2 is positive. The direction of the resultant field at the point shown is approximately represented by the vector labeled ___:

 

 

Ans: 1-c, 2-c, 3-c, 4-a, 5-d, 6-a, 7-b, 8-h

 

 

Physics 236 Worksheet: Chapter 23, Electric Dipole

 

                                                                             Note: In the figure OA = OB = OC = d.

                                                                             Also +q and -q are equidistant from the       

                                                                             origin.

 

 

 

 

1.     The direction of the electric field at point A is

a.     up.

b.      down.

c.      to the right

d.     to the left.

e.     The field here is zero, therefore it has no direction.

2.     The direction of the electric field at point B is

a.     up.

b.      down.

c.      to the right.

d.     to the left.

e.     The field here is zero, therefore it has no direction.

3.     The direction of the electric field at point C is

a.     up.

b.      down.

c.      to the right.

d.     to the left.

e.     The field here is zero, therefore it has no direction.

4.     The direction of the electric field at point O (midpoint of dipole) is

a.     up.

b.      down.

c.      to the right.

d.     to the left.

e.     The field here is zero, therefore it has no direction.

5.     Compare the magnitudes of the fields at points A and B.

a.     The electric field at A is stronger than the field at B.

b.      The electric field at A is weaker than the field at B.

c.      The fields at A and B have equal magnitudes.

6.     Compare the  magnitudes of the fields at points A and O.

a.     The electric field at A is stronger than the field at O.

b.      The electric field at A is weaker than the field at O.

c.      The fields at A and O have equal magnitudes.

7.     At which of the four points is the field the strongest? _____

8.     At which of the four points is the field the weakest? _____

 

Ans: 1-d, 2-c, 3-d, 4-c, 5-a, 6-b, 7-O, 8-B