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:TDIF:Medium
2.Electron flow and conventional current are equal in magnitude, yet opposite in direction.
ANS:TDIF:Medium
3.Because the human body is an infinite supply of electric charges, it is used for the reference of ground.
ANS:FDIF: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:FDIF:Medium
5.Objects can be electrified by induction.
ANS:TDIF:Easy
6.Induction is the process of electrical fields acting on one another with contact.
ANS:FDIF:Easy
7.Electrons flow from greatest potential difference to least potential difference.
ANS:TDIF:Easy
8.For potential difference to exist, there must be electron flow.
ANS:FDIF:Medium
9.As the length of a conductor increases, the resistance increases.
ANS:TDIF:Medium
10.The total resistance of a parallel circuit is always greater than the amount of the highest resistor.
ANS:FDIF:Medium
MULTIPLE CHOICE
1.The resistance in a wire decreases as its diameter ____.
a. / increases / c. / remains the sameb. / decreases / d. / none of the above
ANS:ADIF: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 amperesb. / 1/3 ampere / d. / 27 amperes
ANS:BDIF: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:DDIF:Medium
4.Current is ____.
a. / time/charge / c. / (charge)(time)b. / charge/time / d. / charge/time2
ANS:BDIF:Easy
5.Coulomb's Law of electrical forces is mathematically described as ____.
a. / F = q1q2/r2 / c. / F = q1q2/rb. / F = q/r2 / d. / F = q2/r
ANS:ADIF: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 voltsb. / 1/4 volt / d. / 16 volts
ANS:DDIF:Medium
7.When an electric current flows through a wire with resistance, energy is ____.
a. / liberated as x-rays / c. / liberated as lightb. / liberated as heat / d. / absorbed as heat
ANS:BDIF:Medium
8.Ohm's Law is mathematically described as ____.
a. / C = Q/V / c. / R = V/Ib. / L = -V/It / d. / V = I2R
ANS:CDIF:Medium
9.Electric potential is measured in ____.
a. / coulombs / c. / voltsb. / joules / d. / ohms
ANS:CDIF:Easy
10.Electric insulators ____.
a. / convert electrical energy into heat / c. / inhibit movement of electrical chargeb. / consist of materials like silicon / d. / permit movement of electrical charge
ANS:CDIF:Medium
11.If 20 volts of potential difference causes a current of 5 amperes, the resistance produced is ____.
a. / 1/100 ohm / c. / 4 ohmsb. / 1/4 ohm / d. / 100 ohms
ANS:CDIF:Medium
12.A volt is a measure of ____.
a. / random drift velocity / c. / currentb. / flow rate / d. / potential difference
ANS:DDIF:Easy
13.A charge would lose most of its energy when it passes through a ____.
a. / resistor / c. / generatorb. / battery / d. / all of the above
ANS:ADIF:Medium
14.If the distance between two electrical charges is doubled, the force between them is ____.
a. / decreased by 1/4 / c. / doubledb. / decreased by 1/2 / d. / quadrupled
ANS:ADIF: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 = I2Rb. / P = IR/V / d. / more than one of the above
ANS:DDIF:Medium
16.An ampere is ____.
a. / coulomb/sec / c. / (volt)(ohm)b. / (coulomb)(sec) / d. / ohm/volt
ANS:ADIF:Easy
17.Resistance is ____.
a. / the opposition to the flow of electronsb. / the opposition to the generation of electromotive force
c. / the location of storage of electrons
d. / measured in amperes
ANS:ADIF: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 1/2b. / increased by a factor of 2 / d. / unchanged
ANS:DDIF: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 wattsb. / 8 watts / d. / 1/2 watt
ANS:ADIF:Medium
20.The unit of electrical power is ____.
a. / joule / c. / ampereb. / volt / d. / watt
ANS:DDIF:Easy
21.If 10 coulombs pass a point in 2 seconds, the current is ____.
a. / 0.20 amp / c. / 20 ampsb. / 5 amps / d. / 200 amps
ANS:BDIF:Medium
22.The electrons in an electrical current ____.
a. / all have the same velocityb. / 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:CDIF: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 resistorsb. / the current through each resistor is different
c. / the power dissipated through each resistor is the same
d. / none of the above
ANS:DDIF:Difficult
24.If a conductor is positively charged, it ____.
a. / has too many electrons / c. / has more neutrons than electronsb. / is deficient in electrons / d. / is deficient in protons
ANS:BDIF:Medium
25.The mA is a unit of ____.
a. / EMF / c. / currentb. / voltage / d. / potential difference
ANS:CDIF: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