Electricty 1-7 Ch 2

Question 1

What is the basic function of a switch?

Answer 1

Opening and closing electric circuits

Question 2

What are the three things needed to make an electrical circuit?

Answer 2

1. A power source (power)
2. Connecting wires (conductors)
3. A device using the power to accomplish some purpose (load)

Question 3

In a simple electric circuit, the _____ is the device that takes electrical energy from the power source and uses it to perform some ______ ______.

Answer 3

Load
Useful function

Question 4

What are the two things that the term “load” stands for?

Answer 4

A device that takes power from the source
The power that is taken from the source

Question 5

What is EMF measured in?

Answer 5

Volts

Question 6

The polarity of the voltage source determines what?

Answer 6

The direction the current flows in the circuit

Question 7

The amount of voltage supplied by the voltage source determines what?

Answer 7

The amount of current that will flow through the circuit

Question 8

What are the only two factors that determine how much current will flow in a DC circuit?

Answer 8

The amount of voltage that is supplied by the power source
How well the load in the wires conduct current
(Both is correct answer)

Question 9

What material has the highest conductance?

Answer 9

Silver

Question 10

What is a conductor?

Describe the term conductance

Answer 10

A conductor is a material that allows current to flow easily

Conductance is the ease with which a metal allows current to flow (how well a material allows current to flow)

Question 11

What determines the resistance of any material?

Answer 11

The number of free electrons the material has

Question 12

What determines the resistance of a given conductor?

Answer 12

Increasing the cross-sectional area of a wire decreases its resistance
Increasing the length of the wire increases its resistance

Question 13

How can you produce any kind of resistance affect you want?

Answer 13

Choosing the proper metal for a conductor and making it with a certain cross-section and length

Question 14

What is the unit of resistance and what is the symbol used?

Answer 14

Ohm
Greek letter omega

Question 16

The resistance of a load is ______ ______ than the resistance of the circuit wiring.

Answer 16

Much greater

Question 17

Every power source has some ______ ______.

Answer 17

Internal resistance

Question 18

What is the only way to decrease current?

Answer 18

To add resistance to the circuit

Question 19

What is needed to easily add various amounts of resistance to a circuit without drastically changing physical size or materials used to make it?

Answer 19

Resistors

Question 20

What materials are most often used for resistors?

Answer 20

Carbon
Special metal alloys (such as nichrome, constantan, manganan)

Question 22

What are two possible methods of decreasing large currents in a circuit with a fixed voltage source?

Answer 22

Increasing the resistance of the connecting wires
Adding resistors to the circuit

Question 23

The ______ ______ is usually given as a percentage, and indicates how much higher or lower than the nominal value the actual value of the resistor might be.

Answer 23

Resistor tolerance

Question 24

What does a wattage rating of a resistor determine?

Answer 24

The maximum current a resistor can carry

Question 25

What are three advantages of composition resistors?

Answer 25

Small Rugged Low cost

Question 26

What is the “stability” of a resistor?

Answer 26

The property of maintaining a small tolerance under all operating conditions

Question 27

When all three terminals of a variable resistor are connected into a circuit, the resistor is called a ______.

Answer 27

Potentiometer

Question 28

When only the center terminal and one other terminal are used on a variable resistor in a circuit, the resistor is called a ______.

Answer 28

Rheostat

Question 29

If you raise resistance, current will go ______.

Answer 29

Down

Question 30

What are the three abbreviations for current, voltage, and resistance?

Answer 30

Current ( I ) Voltage ( V ) Resistance ( R )

Question 31

A good practice to always follow is to think in terms of ______ and ______.

Answer 31

Knowns Unknowns

Question 32

What is the definition of “power” ?

Answer 32

The rate at which work is done The amount of work that can be done by a load in some standard amount of time (usually one second)

Question 33

What is the definition of the watt?

Answer 33

1 watt of power is used when 1 ampere flows through the difference of 1 volt

Question 34

The power rating of working equipment is based on what?

Answer 34

Mostly on the power, they can use to do mechanical work

Question 36

Total power used by consumers is sold by the ______-______ by power companies.

Answer 36

Kilowatt-hours

Question 37

1,000,000 V is equal to?

Answer 37

1 Megavolt (megav)

Question 38

What is the definition of volt defined in electrical work?

Answer 38

When an EMF moves one coulomb of electrons (6.28 billion billion electrons) to do one joule of work, the EMF has a potential difference of one volt.

Question 39

What is a series circuit?

Answer 39

When the same amount of current flows through each part of the circuit.

Question 40

When series loads are used, the total circuit resistance is?

Answer 40

The sum of the resistances of each individual loads If a circuit has five loads connected in series and each load is a 10 ohm resistor, the total circuit resistance is 50 ohms

Question 41

How do you connect to batteries in series?

Answer 41

The negative terminal of one connects to the positive terminal of the other

Question 42

What happens to voltage in a series circuit?

Answer 42

All individual voltage sources must be added together

Question 43

The total voltage drop in a series circuit always equals the ______ ______.

Answer 43

Source voltage

Question 44

If power sources are connected so that their polarities are not in the same direction, they will ______ ______ ______.

Answer 44

Oppose each other (Ex. AA batteries in a flashlight must both be facing same direction)

Question 45

If power sources are connected so that their polarities are not in the same direction, they will ______ each other.

Answer 45

Oppose (Ex. AA batteries in a flashlight must both be facing same direction)

Question 46

In which direction does current travel in a series circuit?

Answer 46

From the negative battery terminal, through the circuit, to the positive battery terminal

Question 47

When electron current enters the load, the voltage is ______.

Answer 47

Negative

Question 48

When electron current leaves the load, the voltage is ______.

Answer 48

Positive

Question 49

How is a Short Circuit produced?

Answer 49

When current flows from the negative to the positive terminals of a power source, without going through a load

Question 50

Electromagnetic circuit breaker uses the principle of ______ to open a circuit when too much current flows

Answer 50

Magnetism

Question 51

What is a parallel circuit?

Answer 51

A circuit in which there are one or more points, where the current divides and follows different paths

Question 52

The total current in a parallel circuit is equal to the ______ of the branch currents

Answer 52

Sum

Question 53

In parallel circuit, the total current is ______ to the sum of the branch currents.

Answer 53

Equal

Question 54

The reciprocal method can be used to calculate the ______ ______ of any combination of parallel resistance.

Answer 54

Total resistance

Question 55

The total power consumed is equal to the ______ of the power used by each individual load.

Answer 55

Sum

Question 56

What is Kirchhoff’s first law?

Answer 56

The sum of voltage drops around any closed loop is equal to the sum of the EMF’s in that loop

Question 57

Most resistor failures result from what?

Answer 57

Heat generated in the resistor by current flow