NCATT Direct Current (DC) Terms - Level A

Question 1

Define Direct Current.

Answer 1

Direct Current is the flow of electrons in one direction throughout a circuit with constant voltage and current. Direct current is caused by a constant difference of potential, both negative and positive.

Question 2

Define Electron

Answer 2

Electron is a negatively charged subatomic particles that are located and travel around (orbit) the nucleus in an imaginary sphere or shell at the speed of light (186,000 miles/second). Electrons are involved in the conduction of electricity.

Question 3

Define Proton.

Answer 3

A Proton is a positively charged subatomic particles that exist within the nucleus of all atoms. Protons are not involved in the conduction of electricity.

Question 4

Define Neutron

Answer 4

A Neutron is a neutral subatomic particles that exist within the nucleus of all atoms. Neutrons are not involved in the conduction of electricity.

Question 5

Define Conductor.

Answer 5

A Conductor is the common building block of electrical circuits that easily permits the movement of electrons from an electrical source to a load and back to the electrical source with a minimum of resistance. Resistance depends on such factors as cross sectional area, length, temperature, and conductor material.

Question 6

Define Insulator

Answer 6

Insulator—Material or device used to prevent the passage of heat, electricity, or sound from one medium to another.

Question 7

Define Static Electricity

Answer 7

Static Electricity—Electrical charge that may be built up on a non-conductive surface by friction. Static electricity serves no useful purpose.

Question 8

Define Current

Answer 8

Current—Flow of electricity. Electrical current is the rate of flow of electrons that pass a given point in a specific amount of time.

Question 9

Define Coulomb

Answer 9

Coulomb—Basic unit of electrical quantity. A coulomb is equal to 6.28 billion - billion electrons (6.28 X 10 to the 18th or 6.28 quintillion).

Question 10

Define Ampere

Answer 10

Ampere (A, amp)—Unit of measurement used to express the flow of electrons (current). One amp is the amount of current that can be forced through one ohm of resistance by the pressure of one volt. Current is represented by the international symbol “I”.

Question 11

Define EMF

Answer 11

EMF (E)—Electron moving force measured in volts. EMF is the force causing electrons to move through a conductor.

Question 12

Define Volt

Answer 12

Volt (V)—Basic unit of electrical pressure. A volt is the amount of force required to cause one amp of current to flow through one ohm or resistance. Volt is often expressed by such terms as voltage, voltage drop, potential difference, EMF, or IR drop.

Question 13

Define Resistance

Answer 13

Resistance (R)—Electrical characteristic of a conductor. Opposition that a circuit, component, or substance presents to the flow of electricity. Resistance is force that opposes or slows down another force, drops voltage, and consumes power. Resistance is measured in ohms.

Question 14

Define Ohm’s Law

Answer 14

Ohm’s Law—Ohm’s Law states that “the amount of current flowing in a circuit is directly proportional to the circuit voltage and inversely proportional to the circuit resistance.”

Question 15

Define Ohm

Answer 15

Ohm (Ω)—Unit of electrical opposition to the flow of current. A circuit has one ohm of resistance when it limits the flow of current to one amp under a voltage pressure of one volt.

Question 16

Define Watts

Answer 16

Watts (W)—Basic unit of power that is the product of voltage multiplied by current. One watt (1/746 horsepower) is the power produced in a circuit that has one amp of current flowing under a pressure of one volt.

Question 17

Define Capacitor

Answer 17

Capacitor—Electrical component used to store electrical energy in the form of an electrostatic field. A capacitor is a device made of two parallel conductors separated by an insulator.

Question 18

Define Working Voltage

Answer 18

Working Voltage—Maximum amount of DC voltage that can be safely applied across a capacitor.

Question 19

Define Inductor

Answer 19

Inductor—Coil or other device used to introduce inductance into a circuit. An inductor is a winding, or coiling, of multiple turns of wire.

Question 20

Define Battery

Answer 20

Battery— A device made of one or more individual electrochemical cells used to store chemical energy and make the energy available in the electrical form. There are two categories of batteries, primary and secondary. Batteries can store DC power.

Question 21

Define Left-hand Rule

Answer 21

Left-hand Rule—Refers to generators. This rule is for determining the direction of movement of a current-carrying conductor in a magnetic field.

Question 22

Define Magnetism.

Answer 22

Magnetism—Ability of a magnet to attract certain materials containing iron and to influence electrons. Magnetism is the principal way to effectively produce AC electricity.

Question 23

Define Magnetic Permeability

Answer 23

Magnetic Permeability—Measure of ease that lines of flux travel through a material.

Question 24

Define Scientific Notation

Answer 24

Scientific Notation—Short way of expressing a given number as a number between 1 and 10 multiplied by 10 to the appropriate power.

Question 25

Define Metric Prefixes

Answer 25

Metric Prefixes—Measurements relating or using the metric system of measurement.

Question 26

Define Henry (H).

Answer 26

Henry (H)—Basic unit of measurement for inductance. One Henry is the amount of inductance a current change of one ampere per second induces a voltage of one volt.

Question 27

Define Farad.

Answer 27

Farad—Basic unit of capacitance. One farad holds one coulomb under a pressure of one volt.