Deck 3: Ohms Law, Energy, and Power

Question 1

Power rating for a resistor is mainly based on the physical size.

Answer 1

True

Question 2

If the voltage across a circuit increases, .

A)the current increases
B)the resistance decreases
C)the resistance increases
D)the current decreases

Answer 2

the current increases

Question 3

When taking current measurements, it is extremely important not to accidentally place the meter across the voltage source.

Answer 3

True

Question 4

If a circuit's supply voltage is 20 V and its resistance is 3300 Ω, its current is 6.06 mA.

Question 5

If a circuit's resistance increases, its current decreases.

Question 6

An electronic power supply with a rated current capacity of 500 mA can adequately illuminate a 10 V @ 5 W lamp.

Question 7

Current -sensing resistors are used in

A)computers
B)battery chargers
C)motor controllers
D)all of the above

Question 8

If the current is constant, voltage and resistance are directly proportional.

Question 9

If a 47 kΩ resistor carries 5 mA, it's safe to use a 1 W resistor.

Question 10

If a 1 kΩ resistor has 32 mA flowing through it, it dissipates 1.024 W.

Question 11

If the voltage applied to a circuit doubles, then power dissipation doubles.

Question 12

According to Ohm's Law, if voltage were to decrease while resistance remained the same, current would

A)no way to determine
B)decrease
C)remain the same
D)increase

Question 13

If a circuit's supply voltage is 15 V and its resistance is 4700 Ω, its current is 3.19 mA.

Question 14

If a 56 kΩ resistor carries 10 mA, it is safe to use a 10 W resistor.

Question 15

According to Ohm's Law, if voltage were to increase while resistance remained the same, current would

A)increase
B)no way to determine
C)decrease
D)remain the same

Question 16

Voltage and current are _.

A)quantities that add
B)inversely proportional
C)unrelated
D)directly proportional

Question 17

Braking resistors are

A)designed to fail as an open circuit
B)extremely high -tolerance components
C)very high -power resistors
D)used exclusively in the automotive field

Question 18

If a circuit's resistance decreases, its current also decreases.

Question 19

If a 12 kΩ resistor carries 12 mA, the resistor drops 1 V.

Question 20

If a 2.5 kΩ resistor carries 45 mA, it is dissipating 5.0625 W.

Question 21

If V = 50 V and I = 37 mA in Figure 3 -1, is dissipated by the resistor.

A)1.85 W
B)135 m W
C)1.35 W
D)0.185 m W

Question 22

If the voltage is 15 V and resistance is color coded red -red -brown -silver in Figure 3 -1, what are the maximum and minimum possible current?

A)IMINIMUM = 64.9 mA, IMAXIMUM = 71.8 mA
B)IMINIMUM = 56.8 mA, IMAXIMUM = 85.2 mA
C)IMINIMUM = 62.0 mA, IMAXIMUM = 75.8 mA
D)none of these

Question 23

If voltage is 12 V and the resistance is color -coded brown -black -orange in Figure 3 -1, what are the minimum and maximum possible currents?

A)IMINIMUM = 1 mA, IMAXIMUM = 1.6 mA
B)IMINIMUM = 1.2 mA, IMAXIMUM = 1.4 mA
C)IMINIMUM = 1 mA, IMAXIMUM = 1.5 mA
D)IMINIMUM = 0.8 mA, IMAXIMUM = 1.2 mA

Question 24

If V = 12 V and a 12 kΩ resistor shorts in Figure 3 -1, the current is _ _.

A)0 A
B)1 mA
C)10 mA
D)extremely high

Question 25

If I = 45 mA and R = 40 kΩ in Figure 3 -1, the voltage equals .

A)1.8 V
B)18 V
C)1.125 V
D)1800 V

Question 26

If a 10 kΩ resistor dissipates 0.5 W in Figure 3 -1, then the supply voltage equals _ .

A)70.7 V
B)5000 V
C)50 V
D)7.07 mV

Question 27

If I = 64 mA and R = 470 Ω in Figure 3 -1, the voltage equals .

A)7.34 V
B)30.1 V
C)73.4 V
D)3.01 V

Question 28

If V = 60 V and R = 47 kΩ in Figure 3 -1, the current equals _.

A)1.28 mA
B)128 mA
C)0.128 mA
D)12.8 mA

Question 29

If V = 72 V and I = 12 mA in Figure 3 -1, the resistance equals .

A)47 kΩ
B)6 kΩ
C)864 Ω
D)0.166 Ω

Question 30

If V = 50 V and R = 25 kΩ in Figure 3 -1, the current equals _.

A)50 mA
B)0.5 mA
C)2 mA
D)5 mA

Question 31

If I = 32 mA and R = 469 Ω in Figure 3 -1, the voltage equals .

A)19 V
B)15 V
C)22 V
D)12 V

Question 32

If V = 85 V and I = 15 mA in Figure 3 -1, the resistance equals .

A)1.28 Ω
B)5.67 kΩ
C)52.3 Ω
D)567 Ω

Question 33

If V = 100 V and I = 1 mA in Figure 3 -1, the power dissipated by the resistor equals .

A)10 mW
B)10 W
C)100 mW
D)1 W

Question 34

If the voltage is suddenly switched off in Figure 3 -1, .

A)the current will gradually decrease to 0 A
B)the current will suddenly drop to 0 A
C)the current will first increase and then decrease to 0 A
D)there is no way to predict the current

Question 35

If the resistor opens in Figure 3 -1, the .

A)source voltage decreases to 0 V
B)resistance decreases
C)power dissipation increases
D)circuit current drops to 0 A

Question 36

If I = 64 mA and R = 47 Ω in Figure 3 -1, the voltage equals .

A)73.4 V
B)7.34 V
C)30.1 V
D)3.01 V

Question 37

If the resistor opens in Figure 3 -1, the following circuit conditions would exist.

A)no current flow
B)no power dissipation
C)resistor would read infinite resistance
D)all of the above

Question 38

If V=12V and a 12kΩ resistor were to open in Figure 3 -1, the current is _ _.

A)10 mA
B)0 A
C)1 mA
D)extremely high

Question 39

If V = 25 V and R = 50 kΩ in Figure 3 -1, the current equals _.

A)5 mA
B)50 mA
C)2 mA
D)0.5 mA

Question 40

According to Ohm's Law, if resistance were to decrease while voltage remained the same, current would

A)decrease
B)increase
C)no way to determine
D)remain the same

Question 41

If a resistor is rated at 1/2 W, it .

A)always provides 1/2 W of power
B)can only dissipate more than 1/2 W of power
C)always dissipates 1/2 W
D)can safely dissipate 1/2 W of power

Question 42

If the voltage were suddenly switched on in Figure 3 -1, .

A)the current would gradually decrease and then increase
B)the current would flow
C)the current would gradually decrease
D)the current would be zero

Question 43

If a resistance of 2.2 MΩ is connected across a 1 kV source, current equals about .

A)0.455 mA
B)2.2 mA
C)0.455 A
D)45.5 µA

Question 44

Which is the correct formula for Ohm's Law?

A)R = V × I
B)I = V ÷ R
C)P = V × I
D)V = I ÷ R

Question 45

What is the resistance of a 100 W bulb when it is operating in a circuit with a supply of 120 V?

A)2.14 Ω
B)56 Ω
C)144 Ω
D)560 Ω

Question 46

If I = 27 mA and R = 4.7 Ω in Figure 3 -1, the voltage equals .

A)5.74 V
B)127 mV
C)174 mV
D)7.8 V

Question 47

Resistance and current are _ .

A)not related
B)directly proportional
C)inversely proportional
D)similar to voltage

Question 48

If a resistor that is color -coded yellow -violet -brown -gold is connected to a 12 V source, then what is the current flow?

A)24.3 mA
B)255 mA
C)26.9 mA
D)25.5 mA

Question 49

Which is the correct formula for finding power?

A)P = I2 × R
B)P = V2 ÷ R
C)P = V × I
D)all of these

Question 50

A 250 µA current flowing through a 4.7 kΩ resistor produces a voltage drop.

A)53.2 V
B)18.8 V
C)1.18 V
D)1.18 mV

Question 51

If a resistor that is color -coded yellow -violet -orange -gold is placed across a 15 V source, the resistance and wattage rating could be _.

A)47 kΩ 1/4 W
B)4.7 kΩ 1/8 W
C)0.47 M Ω 1/4 W
D)4700 Ω 1/4 W

Question 52

Which of the following terms is not a resistor rating?

A)resistor value in ohms
B)current
C)resistor tolerance
D)power rating

Question 53

If a resistor that is color -coded red -red -brown -silver is connected to a 15 V source, what is the maximum current that can flow?

A)68.2 mA
B)71.9 mA
C)75.8 mA
D)62 mA

Question 54

Using Watt's law and substituting power can be calculated as .

A)P = I2R
B)P = VI
C)P = V2/R
D)all of these

Question 55

If a 1/2 W resistor is used in the circuit in Figure 3 -1, the current value .

A)is over 12 mA
B)is less than 12 mA
C)depends upon the circuit's voltage and resistance
D)depends upon the voltage applied

Question 56

A 220 Ω 1/2 W resistor has burned open, so you look in your parts box to find a replacement. Which one of the following resistors could you use to repair the circuit?

A)2200 Ω 1/2 W
B)220 Ω 1 W
C)220 Ω 1/4 W
D)220 Ω 1/8 W

Question 57

If a 330 Ω resistor dissipates 2 W, its voltage drop equals .

A)2.57 V
B)25.7 V
C)6.6 V
D)660 V

Question 58

What is the resistance of a 150 W bulb when it is operating in a circuit with a supply of 125 V?

A)2.14 Ω
B)75 Ω
C)9375 Ω
D)104 Ω

Question 59

The power rating of a resistor that must dissipate up to 1.1 W should be .

A)5 W
B)1 W
C)2 W
D)0.25 W

Question 60

If a resistor that is color coded yellow -violet -red is placed across a 25 V source voltage, what value resistor and wattage rating could be used?

A)4700 Ω, 1/4 W
B)470 Ω, 1/2 W
C)47000 Ω, 1/4 W
D)4700 Ω, 1/8 W

Question 61

Which is the most unlikely resistor failure?

A)resistance change
B)shorting
C)opening
D)All are common failures.

Question 62

In the operation of electrical circuits, which, in most cases, is an unwanted by -product?

A)heat
B)mechanical motion
C)light
D)both B and C

Question 63

If the current flow for a given circuit has doubled, then the has been halved.

A)resistance
B)current
C)voltage
D)power

Question 64

Power as it is used in electric circuits can be best defined as:

A)the rate energy is used over time.
B)the rate current flows over time.
C)the rate motion is exerted over time.
D)the rate voltage is applied over time.

Question 65

A kilowatt -hour is best defined as:

A)1,000 watts multiplied by 1 hour.
B)1,000 watts divided by 1 hour.
C)a kilo divided by 1 watt -hour.
D)a kilo multiplied by 1 watt -hour.

Question 66

The voltage of a power supply drops to 0 V when connected to a lamp circuit. What is a possible problem?

A)the lamp is open
B)the lamp requires more current than the power supply can deliver
C)the lamp is shorted
D)both B and C

Question 67

The symbol for a certain amount of energy used over time is .

A)W
B)V
C)P
D)I

Question 68

Typically, which is the first type of measurement taken in a known defective circuit?

A)resistance
B)voltage
C)power
D)current

Question 69

The ampere -hour rating of a battery is defined as the:

A)number of amperes supplied in 1 hour.
B)number of hours per amperes supplied.
C)number of amperes supplied over the number of hours at a given current.
D)all of these.