Deck 23: Electric Current

Question 1

An ampere is a unit of electrical

A)pressure.
B)current.
C)resistance.
D)all of these
E)none of these

Answer 1

current.

Question 2

Stretch a copper wire so that it is thinner and the resistance between its ends

A)decreases.
B)remains unchanged.
C)increases.

Answer 2

increases.

Question 3

When a 10-V battery is connected to a resistor,the current in the resistor is 2 A.What is the resistor's value?

A)2 ohms
B)5 ohms
C)10 ohms
D)20 ohms
E)more than 20 ohms

Answer 3

5 ohms

Question 4

The primary source of electrons in an ordinary electrical circuit is

A)a dry cell,wet cell or battery.
B)the back emf of motors.
C)the power station generator.
D)the electrical circuit itself.
E)none of these

Question 5

Heat a copper wire and its electric resistance

A)decreases.
B)remains unchanged.
C)increases.

Question 6

The source of electrons lighting an incandescent ac light bulb is

A)the power company.
B)electrical outlet.
C)atoms in the light bulb filament.
D)the wire leading to the lamp.
E)the source voltage.

Question 7

The electric power of a lamp that carries 2 A at 120 V is

A)1/6 watts.
B)2 watts.
C)60 watts.
D)20 watts.
E)240 watts.

Question 8

A 10-ohm resistor has a 5-A current in it.What is the voltage across the resistor?

A)5 V
B)10 V
C)15 V
D)20 V
E)more than 20 V

Question 9

Electrons move in an electrical circuit

A)by being bumped by other electrons.
B)by colliding with molecules.
C)by interacting with an established electric field.
D)because the wires are so thin.
E)none of these

Question 10

A woman experiences an electrical shock.The electrons making the shock come from the

A)woman's body.
B)ground.
C)power plant.
D)hairdryer.
E)electric field in the air.

Question 11

Electrons are made to flow in a wire when there is

A)an imbalance of charges in the wire.
B)more potential energy at one end of the wire than the other.
C)a potential difference across its ends.

Question 12

When a light switch is turned on in a dc circuit,the average speed of electrons in the lamp is

A)the speed of sound waves in metal.
B)the speed of light.
C)1000 cm/s.
D)less than 1 cm/s.
E)dependent on how quickly each electron bumps into the next electron.

Question 13

A coulomb of charge that passes through a 6-volt battery is given

A)6 joules.
B)6 amperes.
C)6 ohms.
D)6 watts.
E)6 newtons.

Question 14

In a common dc circuit,electrons move at speeds of

A)a fraction of a centimeter per second.
B)many centimeters per second.
C)the speed of a sound wave.
D)the speed of light.
E)none of these

Question 15

The current through a 10-ohm resistor connected to a 120-V power supply is

A)1 A.
B)10 A.
C)12 A.
D)120 A.
E)none of these

Question 16

Alternating current is normally produced by a

A)battery.
B)generator.
C)both of these
D)neither of these

Question 17

A wire carrying a current is normally charged

A)negatively.
B)positively.
C)not at all.

Question 18

A wire that carries an electric current

A)is electrically charged.
B)may be electrically charged.
C)is never electrically charged.

Question 19

In an ac circuit,the electric field

A)increases via the inverse-square law.
B)changes magnitude and direction with time.
C)is the same everywhere.
D)is non-existent.
E)none of these

Question 20

Which statement is correct?

A)Charge flows in a closed circuit.
B)Voltage flows through an open or a closed circuit.
C)Resistance flows through an open circuit.
D)Current is the primary cause of voltage.

Question 21

An electrical diode is useful for

A)storing electrical energy.
B)boosting voltage.
C)limiting current.
D)voltage modification.
E)changing ac to dc.

Question 22

On some early automobiles both headlights went out when one bulb burned out.The headlights must have been connected in

A)parallel.
B)perpendicular.
C)series.
D)haste.

Question 23

A 100-Watt lamp glows brighter than a 25-Watt lamp.The electrical resistance of the 100-Watt lamp must be

A)less.
B)greater.
C)the same.

Question 24

A circuit breaker often serves the same purpose as a

A)battery
B)fuse.
C)capacitor.
D)All of the above choices are correct.
E)None of the above choices are correct.

Question 25

The number of electrons delivered daily to an average American home by an average power utility in the mid 1980s was

A)zero.
B)110.
C)220.
D)billions of billions.
E)none of these

Question 26

Two lamps,one with a thick filament and one with a thin filament of the same material,are connected in parallel to a battery.The current is

A)larger in the lamp with the thick filament.
B)larger in the lamp with the thin filament.
C)the same in both lamps.

Question 27

In an electric circuit,the safety fuse is connected to the circuit in

A)series.
B)parallel.
C)either series or parallel.

Question 28

A capacitor is useful in

A)boosting the energy output of a circuit.
B)increasing the current in a resistor.
C)smoothing pulsed current.
D)switching dc to ac in a circuit.
E)increasing or decreasing voltage.

Question 29

A capacitor is used to store

A)both charge and energy.
B)energy.
C)charge.
D)neither charge nor energy.

Question 30

There are electrons in the filament of the ac lamp in your bedroom.When you turn on the lamp and it glows,the glowing comes from

A)different electrons;the ones that flow in the circuit to your lamp.
B)the same electrons.
C)the positive charges that flow in the filament.

Question 31

Two lamps,one with a thick filament and one with a thin filament of the same material,are connected in series to a battery.The voltage is

A)greater across the lamp with the thick filament.
B)greater across the lamp with the thin filament.
C)the same for both lamps.

Question 32

In a 110-volt circuit containing a lamp in series with the voltage source

A)110 coulombs of charge flow through the lamp every second.
B)110 joules of energy are converted to heat and light in the circuit every second.
C)110 joules of energy are given up by each coulomb of charge making up the current in the circuit.
D)110 joules of energy are shared among all the coulombs in the circuit at any instant.
E)none of the above

Question 33

As more lamps are put into a series circuit,the overall current in the power source

A)increases.
B)decreases.
C)stays the same.

Question 34

When two lamps are connected in parallel to a battery,the electrical resistance that the battery senses is

A)more than the resistance of either lamp.
B)less than the resistance of either lamp.
C)none of these

Question 35

When two 1-ohm resistors are connected in series,their combined resistance is

A)1 ohm,and when connected in parallel,2 ohms.
B)2 ohms,and when in parallel,1 ohm.
C)1/2 ohm,and when in parallel,2 ohms.
D)2 ohms,and when in parallel,1/2 ohm.
E)none of these

Question 36

Two lamps,one with a thick filament and one with a thin filament,are connected in parallel to a battery.The voltage is

A)greatest across the lamp with the thick filament.
B)greatest across the lamp with the thin filament.
C)the same in both lamps.

Question 37

Two lamps,one with a thick filament and one with a thin filament,are connected in series.The current is

A)greater in the lamp with the thick filament.
B)greater in the lamp with the thin filament.
C)the same in each lamp.

Question 38

In a simple circuit containing a bulb,energy is given to the moving charges by

A)the bulb.
B)the wires.
C)a generator.
D)none of these

Question 39

When two lamps are connected in series to a battery,the electrical resistance that the battery senses is

A)more than the resistance of either lamp.
B)less than the resistance of either lamp.
C)none of these

Question 40

Modern automobile headlights are connected in

A)parallel.
B)perpendicular.
C)series.
D)none of these

Question 41

A power line with a resistance of 2 ohms has a current of 80 A in it.The power dissipated in the line is

A)40 W.
B)160 W.
C)320 W.
D)12,800 W.
E)none of these

Question 42

An electric heater is rated at 300 W when used in a 110-V circuit.The safety fuse in the circuit can handle 15 A of current.How many heaters can be safely operated in the circuit?

A)2
B)3
C)4
D)5
E)more than 5

Question 43

As more lamps are put into a parallel circuit,the overall current in the power source

A)increases.
B)decreases.
C)stays the same.

Question 44

If 0.8 A of current flow through a light bulb connected to a 120 V outlet,the power consumed is

A)12 W.
B)15 W.
C)60 W.
D)96 W.
E)120 W.

Question 45

A circuit is powered with a battery.Charge flows

A)out of the battery and into the circuit.
B)from the negative battery terminal to the positive terminal.
C)only after a couple seconds pass.
D)through both the battery and the rest of the circuit.
E)none of these

Question 46

If you plug an electric toaster rated at 110 V into a 220-V outlet,the current in the toaster will be about

A)half what it should be.
B)the same as if it were plugged into 110 V.
C)more than twice what it should be.
D)twice what it should be.

Question 47

Which is more dangerous,touching a faulty 110-volt light fixture,or a Van de Graaff generator charged to 100,000 volts?

A)touching the light fixture
B)touching the generator
C)Touching both are about equally dangerous.

Question 48

When a 60-watt light bulb is connected to a 120-volt source the current in the light bulb is

A)0)25 A.
B)0)5 A.
C)2 A.
D)4 A.
E)more than 4 A.

Question 49

Compared to a single lamp connected to a battery,two identical lamps connected in series to the same battery will carry

A)more current.
B)less current.
C)the same current.

Question 50

The power dissipated in a 4-ohm resistor carrying 3 A is

A)7 W.
B)18 W.
C)36 W.
D)48 W.
E)not enough information to say

Question 51

Compared to the resistance of two resistors connected in series,the same two resistors connected in parallel have

A)more resistance.
B)less resistance.
C)the same resistance.

Question 52

A 4-ohm resistor is connected in parallel with a 6-ohm resistor.This combination produces an equivalent resistance of

A)2)4 ohms.
B)4 ohms.
C)5 ohms.
D)5)5 ohms.
E)10 ohms.

Question 53

Compared to a single lamp connected to a battery,two lamps connected in parallel to the same battery will carry

A)more current.
B)less current.
C)the same current.

Question 54

A 60-W light bulb and a 100-W light bulb are connected in series to a 120 V outlet.Which light bulb has more current in it?

A)the 60-W bulb
B)the 100-W bulb
C)Both have the same current.

Question 55

A 60-W light bulb and a 100-W light bulb are each rated at 120 V.Which light bulb has a larger resistance?

A)the 60-W bulb
B)the 100-W bulb
C)Both have the same resistance.

Question 56

A heater uses 20 A when used in a 110-V line.If electric power costs 10 cents per kilowatt hour,the cost of running the heater for 10 hours is

A)$0.22.
B)$0.55.
C)$2.20.
D)$5.50.
E)none of these

Question 57

When we say an appliance "uses up electricity," we really are saying that

A)current disappears.
B)electric charges are dissipated.
C)the main power supply voltage is lowered.
D)electrons are removed from the circuit and placed elsewhere.
E)electron kinetic energy is changed into heat.

Question 58

The headlights,radio,and defroster fan in an automobile are connected in

A)series with a switch for each.
B)parallel with a switch for each.
C)series without separate switches.
D)parallel without separate switches.

Question 59

Compared to the filament thickness of a 60-W light bulb,the filament of a 100-W light bulb will be

A)thinner.
B)thicker.
C)the same.

Question 60

The current through two identical light bulbs connected in series is 0.25 A.The voltage across both bulbs is 110 V.The resistance of a single light bulb is

A)22 ohms.
B)44 ohms.
C)220 ohms.
D)440 ohms.
E)none of these

Question 61

What is the resistance of a 120-W incandescent lamp connected to a 120-V power supply?

A)1 ohm
B)60 ohms
C)100 ohms
D)144 ohms
E)none of these

Question 62

Connect a pair of lamps in series and you draw current from the connected battery.Connect the same lamps in parallel and you draw

A)the same current.
B)more current.
C)less current.
D)sometimes more,sometimes less.

Question 63

The ratio of the potential difference across a metallic conductor to the current in the conductor is known as

A)potential drop.
B)conductivity.
C)resistance.
D)electromagnetic force.
E)None of the above choices are correct.

Question 64

A sphere has a negative charge of 6.4 × 10-7 coulomb.The approximate number of electrons that must be removed to make the sphere neutral is

A)1)6 × 10-8.
B)9)8 × 103.
C)6)4 × 1026.
D)4)0 × 1012.

Question 65

Compared to the amount of electric current in the filament of a lamp,the amount of current in the connecting wire is

A)definitely less.
B)often less.
C)actually more.
D)the same.
E)incredibly,all of these

Question 66

What condition must exist between two points in a conductor in order to maintain a flow of charge?

A)a steady magnetic field
B)a high resistance
C)a switch connected in series
D)All of the above choices are correct.
E)None of the above choices are correct.

Question 67

Three resistors,1-ohm,2-ohm,and 3- ohm are connected in parallel.If they were connected in series instead their equivalent resistance would be

A)7 times as great.
B)9 times as great.
C)11 times as great.
D)13 times as great.
E)None of the above choices are correct.