Download chapter 3—electricity

CHAPTER 3—ELECTRICITY
TRUE/FALSE
1. As two electrical charges move further apart, the force between them decreases proportionally to the
inverse square of their separation.
ANS: T
DIF: Medium
2. Electron flow and conventional current are equal in magnitude, yet opposite in direction.
ANS: T
DIF: Medium
3. Because the human body is an infinite supply of electric charges, it is used for the reference of ground.
ANS: F
DIF: Medium
4. The force between two charges is inversely proportional to the product of their magnitudes and
directly proportional to the square of the distances between them.
ANS: F
DIF: Medium
5. Objects can be electrified by induction.
ANS: T
DIF: Easy
6. Induction is the process of electrical fields acting on one another with contact.
ANS: F
DIF: Easy
7. Electrons flow from greatest potential difference to least potential difference.
ANS: T
DIF: Easy
8. For potential difference to exist, there must be electron flow.
ANS: F
DIF: Medium
9. As the length of a conductor increases, the resistance increases.
ANS: T
DIF: Medium
10. The total resistance of a parallel circuit is always greater than the amount of the highest resistor.
ANS: F
DIF: Medium
MULTIPLE CHOICE
1. The resistance in a wire decreases as its diameter ____.
a. increases
c. remains the same
b. decreases
d. none of the above
ANS: A
DIF: Medium
2. If the total resistance in a circuit is 9 ohms and the total voltage is 3 volts, the current is ____.
a. 1/27 ampere
c. 3 amperes
b. 1/3 ampere
d. 27 amperes
ANS: B
DIF: Medium
3. If a DC circuit is ____.
a. in series, the currents are different for each component (e.g., resistors)
b. in series, the voltages are the same for each component
c. in parallel, the currents are equal for all paths of the circuit
d. in parallel, the voltages are equal for all paths of the circuit
ANS: D
DIF: Medium
4. Current is ____.
a. time/charge
b. charge/time
ANS: B
c. (charge)(time)
d. charge/time2
DIF: Easy
5. Coulomb's Law of electrical forces is mathematically described as ____.
a. F = q1q2/r2
c. F = q1q2/r
2
b. F = q/r
d. F = q2/r
ANS: A
DIF: Medium
6. A current of 2 amperes and a resistance of 8 ohms require what voltage in a circuit?
a. 1/16 volt
c. 4 volts
b. 1/4 volt
d. 16 volts
ANS: D
DIF: Medium
7. When an electric current flows through a wire with resistance, energy is ____.
a. liberated as x-rays
c. liberated as light
b. liberated as heat
d. absorbed as heat
ANS: B
DIF: Medium
8. Ohm's Law is mathematically described as ____.
a. C = Q/V
c. R = V/I
b. L = -V/It
d. V = I2R
ANS: C
DIF: Medium
9. Electric potential is measured in ____.
a. coulombs
b. joules
ANS: C
DIF: Easy
10. Electric insulators ____.
a. convert electrical energy into heat
b. consist of materials like silicon
ANS: C
c. volts
d. ohms
DIF: Medium
c. inhibit movement of electrical charge
d. permit movement of electrical charge
11. If 20 volts of potential difference causes a current of 5 amperes, the resistance produced is ____.
a. 1/100 ohm
c. 4 ohms
b. 1/4 ohm
d. 100 ohms
ANS: C
DIF: Medium
12. A volt is a measure of ____.
a. random drift velocity
b. flow rate
ANS: D
c. current
d. potential difference
DIF: Easy
13. A charge would lose most of its energy when it passes through a ____.
a. resistor
c. generator
b. battery
d. all of the above
ANS: A
DIF: Medium
14. If the distance between two electrical charges is doubled, the force between them is ____.
a. decreased by 1/4
c. doubled
b. decreased by 1/2
d. quadrupled
ANS: A
DIF: Medium
15. A formulation of power in a circuit with an EMF source and a resistor with a current is ____.
a. P = IV
c. P = I2R
b. P = IR/V
d. more than one of the above
ANS: D
DIF: Medium
16. An ampere is ____.
a. coulomb/sec
b. (coulomb)(sec)
ANS: A
c. (volt)(ohm)
d. ohm/volt
DIF: Easy
17. Resistance is ____.
a. the opposition to the flow of electrons
b. the opposition to the generation of electromotive force
c. the location of storage of electrons
d. measured in amperes
ANS: A
DIF: Easy
18. The charge on each of two objects is doubled and they are moved twice as far apart. The force between
them is ____.
a. increased by a factor of 4
c. increased by a factor of 1/2
b. increased by a factor of 2
d. unchanged
ANS: D
DIF: Medium
19. A circuit has a current of 2 amperes and a resistance of 4 ohms. The maximum power that can be
delivered is ____.
a. 16 watts
c. 2 watts
b. 8 watts
d. 1/2 watt
ANS: A
DIF: Medium
20. The unit of electrical power is ____.
a. joule
b. volt
ANS: D
c. ampere
d. watt
DIF: Easy
21. If 10 coulombs pass a point in 2 seconds, the current is ____.
a. 0.20 amp
c. 20 amps
b. 5 amps
d. 200 amps
ANS: B
DIF: Medium
22. The electrons in an electrical current ____.
a. all have the same velocity
b. flow from one end of the circuit to another
c. have a net motion in the direction opposite to the conventional current flow
d. none of the above
ANS: C
DIF: Medium
23. In a battery circuit with several resistors of different values connected in series ____.
a. the voltage drop is the same across all the resistors
b. the current through each resistor is different
c. the power dissipated through each resistor is the same
d. none of the above
ANS: D
DIF: Difficult
24. If a conductor is positively charged, it ____.
a. has too many electrons
b. is deficient in electrons
ANS: B
DIF: Medium
25. The mA is a unit of ____.
a. EMF
b. voltage
ANS: C
c. has more neutrons than electrons
d. is deficient in protons
c. current
d. potential difference
DIF: Easy
PROBLEM
1. If a circuit has potential difference of 80 kV and a current of 400 mA, what is the resistance?
ANS:
2.0 × 105 ohms
DIF: Difficult
2. A 100 watt light bulb operates on 120-volt household voltage. How much current does the light bulb
draw?
ANS:
0.83 amp
DIF: Difficult
3. How much resistance does the bulb offer?
ANS:
144.6 ohms
DIF: Difficult
4. What is the total resistance of a circuit with two resistances of 3 and 5 ohms in series and two
resistances of 4 ohms each in parallel?
ANS:
10 ohms
DIF: Difficult
5. Calculate the current supplied to a circuit with two resistances of 3 and 5 ohms in series and two
resistances of 4 ohms each in parallel.
ANS:
2 amperes
DIF: Difficult