Deck 4: Energy and Power

Question 1

Express 0.15 mW as µW.

A) 0.00015 µW
B) 15 µW
C) 1.5 µW
D) 150 µW

Answer 1

150 µW

Question 2

The amount of voltage in a circuit is 50 V, while the current is 0.2 mA. Determine the power.

A) 250 W
B) 0.01 W
C) 2 W
D) 10 W

Answer 2

0.01 W

Question 3

Power is the rate at which energy is used.

Answer 3

True

Question 4

The collision of electrons when passing through resistance results in energy loss given off as:

A) watts
B) light
C) heat
D) voltage

Question 5

Power is measured in:

A) Amperes
B) Watts
C) Joules
D) Energy

Question 6

The amount of current in a circuit is 10 mA, while the resistance is 1 kΩ. Determine the power.

A) 0.0001 W
B) 10 W
C) 100 W
D) 0.1 W

Question 7

How many Watts are used when 6000 Joules of energy are consumed in 5 hours?

A) 6000 W
B) 1200 W
C) 0.33 W
D) 200 W

Question 8

Which of the following is NOT a correct formula for calculating power?

A) P = V2/R
B) P = IV
C) P = I2R
D) P = VR

Question 9

Convert 0.072 W to mW.

A) 0.000072 mW
B) 72 mW
C) 7.2 mW
D) 720 mW

Question 10

Voltage in a circuit is 100 V, the resistance is 10 kΩ. Determine the power.

A) 1 W
B) 0.1 W
C) 10 W
D) 0.01 W

Question 11

A 1 kW load that operates for 1 hour consumes the same amount of energy as a 100 W load that operates for 10 hours.

Question 12

The power dissipated by a resistor doubles if the applied voltage doubles.

Question 13

One Watt equals one Joule per second.

Question 14

Voltage forces electrical energy through a circuit.

Question 15

Efficiency is determined by dividing the power output by the power input.

Question 16

If 50 Joules are used in ten seconds, the power will be 500 Watts.

Question 17

Power companies charge for energy used on the basis of:

A) Wh
B) kW
C) kWh
D) MWh

Question 18

The symbol for power is:

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

Question 19

Energy is the ability to do work.

Question 20

The rate at which work is performed is called power.

Question 21

A 12 V battery is connected to a 400 Ω load. If it supplied current for 1000 hours, what was its Ah rating?

A) 30 Ah
B) 120 Ah
C) 3 Ah
D) 60 Ah

Question 22

Figure 4-1
Given the circuit in Figure 4-1, the power consumed by the lamp is:

A) 220 W
B) 14 W
C) 144 W
D) 100 W

Question 23

Given the circuit in Figure 4-3, which of the following resistor power values would you use in the circuit?

A) 1 W
B) 5 W
C) 15 W
D) 20 W

Question 24

If one needed a very high power rating, an appropriate choice for the resistor would be:

A) metal-film
B) carbon-composition
C) wire wound
D) carbon-film

Question 25

How many joules of energy will a 10 W lamp dissipate in one minute?

A) 60 joules
B) 600 joules
C) 10 joules
D) 3600 joules

Question 26

One kilowatt-hour is equivalent to:

A) 1.0 × 103 joules
B) 3.6 × 105 joules
C) 3.6 × 106 joules
D) 60 × 104 joules

Question 27

How long would it take for a 60 W lamp to consume 30.24 kilowatt-hours of power?

A) 3 weeks
B) 0.505 hours
C) 3 hours
D) 21 hours

Question 28

The change in energy from one end of a resistor to another creates:

A) voltage loss
B) voltage gain
C) voltage rise
D) voltage drop

Question 29

Given the circuit in Figure , what is the resistance of the lamp?

A) 120 Ω
B) 1.2 Ω
C) Not enough data to calculate the resistance
D) 12 Ω

Question 30

What is the total dissipated power from two series-connected 100 W lamps?

A) 10 kW
B) 50 W
C) 100 W
D) 200 W

Question 31

If a 12 Ω draws 1 A of current, what should be its wattage rating?

A) 1/4 W
B) 1.2 W
C) 3/4 W
D) 12 W

Question 32

A power supply provides a continuous 200 W to a load, with an efficiency of 80%. In a 24-hour period, how many KWh of energy does it consume?

A) 600 KWh
B) 4.8 KWh
C) 250 KWh
D) 6 KWh

Question 33

How much power does a 50 V amplifier use when 5 A of current flows through it?

A) 250 mW
B) 10 W
C) 250 W
D) 100 mW

Question 34

A resistor which has a large physical size means:

A) it can handle less power
B) it can dissipate more heat
C) it contains more carbon
D) it contains more resistance in ohms

Question 35

50 mA of current flows through a 10 kΩ resistor. How much power is dissipated?

A) 25 mW
B) 5 µW
C) 0.25 µW
D) 25 W

Question 36

A system with an input power of 50 W and an output of 20 W has an efficiency of:

A) 50%
B) 20%
C) 25%
D) 40%

Question 37

A 5.1 kΩ resistor has burned out in a circuit. You are to replace it with one of like ohmic value. If the resistor should carry 15 mA, which of the following standard resistors should one use?

A) 5.1 kΩ, 5 W
B) 5.1 kΩ, 1 W
C) 5.1 kΩ, 1/2 W
D) 5.1 kΩ, 2 W

Question 38

If you installed a 33 Ω, 1 watt resistor in the circuit in Figure , the resistor will probably:

A) burn up
B) work fine
C) produce a little heat
D) short

Question 39

The maximum amount of power a resistor can safely handle without damage is called:

A) power rating
B) watts
C) heat
D) surface area

Question 40

Given the circuit in Figure 4-2, the power delivered to the lamp is:

A) 1.0 W
B) 12 W
C) 120 W
D) 1.2 W

Question 41

A voltage drop is:

A) called a difference of potential
B) the comparison of energy lost from one end of a resistance to the other
C) the loss of energy by electrons as they flow through a resistance
D) all of the above

Question 42

If a lamp transforms 120 joules of energy into light and heat every 2 seconds, how much power does it use?

A) 240 W
B) 480 W
C) 120 W
D) 60 W

Question 43

For a circuit that contains a 50 V power supply and a 100 Ω resistor, what power rating should be assigned to the resistor?

A) 250 W
B) 25 W
C) 2.5 W
D) 125W

Question 44

What is the kilowatt-hour consumption of a 40 W lamp if it remains "on" for 1750 hours?

A) 70.00
B) 43.75
C) 43,750
D) 70,000

Question 45

Which of the following is a correct formula for calculating power?

A) $P=\frac{V^{2}}{R}$

B) $P=E V$

C) $\mathrm{P}=\mathrm{WI}$

D) $\mathrm{P}=\mathrm{IR} ^2$

Question 46

The length of time that a battery can deliver a certain amount of average current to a load at the rated voltage is called the:

A) ampere-hour rating
B) current rating
C) minimum power rating
D) voltage rating

Question 47

The power rating of a resistor is related to .

A) directly, the type of cooling used
B) directly, its surface area
C) indirectly, the type of material used

Question 48

What value of power is dissipated by a 5 kΩ resistor, when 30 nA flows through it?

A) 6.67 mW
B) 150 W
C) 6 nW
D) 4.5 pW

Question 49

How much energy does a 6 V battery have when it stores 12 coulombs of charge?

A) 5 joules
B) 2 joules
C) 432 joules
D) 72 joules