Review Exercise Solution

Section 1a: Multiple-Choice on Chapter 17 - Electric Potential

Circle the correct answer (one correct answer for each problem)

 

1)  Which of the following is not a vector?

 

     A) electric force

     B) electric field

     C) electric potential

     D) electric line of force

Answer: C

 

2)  For an electron moving in a direction opposite to the electric field

 

     A) its potential energy increases and its electric potential decreases.

     B) its potential energy decreases and its electric potential increases.

     C) its potential energy increases and its electric potential increases.

     D) its potential energy decreases and its electric potential decreases.

Answer: B

 

3)  A small charged ball is accelerated from rest to a speed v by a 500 V potential difference. 

     If the potential difference is changed to 2000 V, what will the new speed of the ball be?

 

     A) v

     B) 2v

     C) 4v

     D) 16v

Answer: B

 

4)  A surface on which all points are at the same potential is referred to as  

 

     A) a constant electric force surface.

     B) a constant electric field surface.

     C) an equipotential surface.

     D) an equivoltage surface.

Answer: C

 

5)  A negative charge is moved from point A to point B along an equipotential surface.

 

     A) The negative charge performs work in moving from point A to point B.

     B) Work is required to move the negative charge from point A to point B.

     C) Work is both required and performed in moving the negative charge from point A to

          point B.

     D) No work is required to move the negative charge from point A to point B.

Answer: D

 

6)  The electron-volt is a unit of

 

     A) voltage.

     B) current.

     C) power.

     D) energy.

Answer: D

 

7)  The absolute potential at a distance of 2.0 m from a positive point charge is 100 V.  What

     is the absolute potential 4.0 m away from the same point charge?

 

     A) 25 V

     B) 50 V

     C) 200 V

     D) 400 V

Answer: B

 

8)  Electric dipoles always consist of two charges that are

 

     A) equal in magnitude; opposite in sign.

     B) equal in magnitude; both are negative.

     C) equal in magnitude; both are positive.

     D) unequal in magnitude; opposite in sign.

Answer: A

 

9)  Two parallel-plate capacitors are identical in every respect except that one has twice the

     plate area of the other.  If the smaller capacitor has capacitance C, the larger one has

     capacitance

 

     A) C/2.

     B) C.

     C) 2C.

     D) 4C.

Answer: C

 

10)  A battery charges a parallel-plate capacitor fully and then is removed.  The plates are

       immediately pulled apart.  (With the battery disconnected, the amount of charge on the    

       plates remains constant.)  What happens to the potential difference between the plates

       as they are being separated?

 

      A) It increases.

      B) It decreases.

      C) It remains constant.

      D) cannot be determined from the information given

Answer: A

 

11)  A parallel-plate capacitor is connected to a battery and becomes fully charged.  The

       capacitor is then disconnected, and the separation between the plates is increased in

       such a way that no charge leaks off.  The energy stored in this capacitor has

 

      A) increased.

      B) decreased.

      C) not changed.

      D) become zero.

Answer: A

 

12)  Doubling the capacitance of a capacitor holding a constant charge causes the energy

       stored in that capacitor to

 

      A) quadruple.

      B) double.

      C) decrease to one half.

      D) decrease to one fourth.

Answer: D

 

13)  Doubling the voltage across a given capacitor causes the energy stored in that capacitor

       to

 

      A) quadruple.

      B) double.

      C) reduce to one half.

      D) reduce to one fourth.

Answer: A

 

 

Section 1b: Multiple-Choice on Chapter 18 - Electric Currents

Circle the correct answer (one correct answer for each problem)

 

1)  A device that produces electricity by transforming chemical energy into electrical energy is

     called a  

 

     A) generator.

     B) transformer.

     C) battery.

     D) none of the given answers

Answer: C

 

2)  A car battery

 

     A) has an emf of 6 V consisting of one 6-V cell.

     B) has an emf of 6 V consisting of three 2-V cells connected in series.

     C) has an emf of 6 V consisting of three 2-V cells connected in parallel.

     D) has an emf of 12 V consisting of six 2-V cells connected in series.

Answer: D

 

3)  Car batteries are rated in "amp-hours."  This is a measure of their

 

     A) charge.

     B) current.

     C) emf.

     D) power.

Answer: A

 

4)  The resistance of a wire is defined as

 

     A) (current)*(voltage).

     B) (current)/(voltage).

     C) (voltage)/(current).

     D) none of the given answers

Answer: C

 

5)  The resistance of a wire is  

 

     A) proportional to its length and its cross-sectional area.

     B) proportional to its length and inversely proportional to its cross-sectional area.

     C) inversely proportional to its length and proportional to its cross-sectional area.

     D) inversely proportional to its length and its cross-sectional area.

Answer: B

 

6)  The resistivity of a wire depends on

 

     A) its length.

     B) its cross-sectional area.

     C) the material out of which it is composed.

     D) all of the given answers

Answer: C

 

7)  The length of a wire is doubled and the radius is doubled.  By what factor does the

      resistance change?

 

     A) four times as large

     B) twice as large

     C) half as large

     D) quarter as large

Answer: C

 

8)  How much more resistance does a 1.0 cm diameter rod have compared to a 2.0 cm

     diameter rod of the same length and made of the same material?

 

     A) 75%

     B) 100%

     C) 300%

     D) 400%

Answer: C

 

9)  What is 1 W equivalent to?

 

     A) 1 V/A

     B) 1 Ω∙A

     C) 1 V∙A

     D) 1 V/Ω

Answer: C

 

10)  If the resistance in a constant voltage circuit is doubled, the power dissipated by that

       circuit will

 

     A) increase by a factor of two.

     B) increase by a factor of four.

     C) decrease to one-half its original value.

     D) decrease to one-fourth its original value.

Answer: C

 

11)  Consider two copper wires each carrying a current of 3.0 A.  One wire has twice the

       diameter of the other.  The ratio of the drift velocity in the smaller diameter wire to that in

       the larger diameter wire is

 

     A) 4:1.

     B) 2:1.

     C) 1:2.

     D) 1:4.

Answer: A

 

12)  Materials in which the resistivity becomes essentially zero at very low temperatures are

       referred to as  

 

     A) conductors.

     B) insulators.

     C) semiconductors.

     D) superconductors.

Answer: D

 

Section 2: Extra Credit

 

In the Fluids section of my manual, I provide portraits of and discuss some of the important pioneers. Identify each of these pioneers by placing their last name below their portrait. A hint is provided for each.

 

 

 

A. Despite his mathematical prowess, he is perhaps best remembered for an incident

     involving the crown of King Hiero.

B. His theorem states that the speed, v, of a fluid through a hole at the bottom of a tank filled

     to a depth h is the same as the speed that a body (in this case a drop of water) would

     acquire in falling freely from a height h, i.e. v = (2gh)^1/2  where g is the acceleration due to

     gravity.

C. His principle states that if If an external pressure is applied to a confined fluid, the pressure

     at every point within the fluid increases by that amount.

D. His principle states that where the velocity of a fluid is high, the pressure is low, and where

     the velocity is low,a the pressure is high.

E. He was an Italian physicist and the discoverer of the_____ effect; the _____pump and

     _____tube are named after him.