3.3 Electrical Terminology

Question 2

What is the SI unit for voltage?

Answer 2

Volt (V)

Voltage is defined as the number of joules of energy per coulomb of charge.

Question 3

What does EMF stand for in electrical measurements?

Answer 3

Electromotive Force

EMF is equal to the terminal potential difference when no current flows.

Question 4

What is the difference between DC voltage and AC voltage?

Answer 4

DC voltage maintains the same polarity over time; AC voltage changes magnitude and polarity over time.

Question 5

What is the symbol used for electric current?

Answer 5

I

The ampere is the unit for measuring electric current.

Question 6

What is the SI unit for electric current?

Answer 6

Ampere (A)

1 ampere = 6.24 × 10^18 electrons/second.

Question 7

Fill in the blank: The higher the __________ of the supply, the higher the current will be for a given electrical resistance.

Answer 7

EMF

Question 8

What does electrical resistance measure?

Answer 8

Opposition to the flow of electric current.

Question 9

What is the SI unit for resistance?

Answer 9

Ohm (Ω)

Question 10

How does the shape of a conductor affect resistance?

Answer 10

Resistance increases where conducting material narrows.

Question 11

What is electrical conductance?

Answer 11

The effectiveness of current conduction, measured in Siemens (S).

Question 12

What is the relationship between conductance and resistance?

Answer 12

Conductance is the reciprocal of resistance.

Question 13

What is the symbol for electrical charge?

Answer 13

Q

The unit for electrical charge is the Coulomb (C).

Question 14

Fill in the blank: 1 coulomb = 1 __________.

Answer 14

ampere-second

Question 15

What is conventional current flow?

Answer 15

The flow direction of positive charges from the positive to the negative pole.

Question 16

What is the difference between conventional current flow and electron flow?

Answer 16

Conventional current flow is from positive to negative, while electron flow is from negative to positive.

Question 17

What is the purpose of a voltmeter?

Answer 17

To measure voltage across two points in a circuit.

Question 18

Common voltage for typical aircraft AC power?

Answer 18

115 V

Question 19

Common voltage for typical aircraft DC power?

Answer 19

28 V

Question 20

What happens when a voltage is applied across a conductor?

Answer 20

Electrons move from the negative to the positive pole.

Question 21

How is electrical charge (Q) calculated?

Answer 21

Q = I × t

Where I is current in amperes and t is time in seconds.

Question 22

What is the effect of collisions between electrons and ions in a conductor?

Answer 22

Electrons lose speed, causing a rise in temperature of the conductor.

Question 23

What are common current ratings for electrical appliances in households?

Answer 23

100 mA/50 A

Question 24

What is the decimal factor for the SI prefix ‘mega’?

Answer 24

1 000 000 (10^6)

Question 25

What is the voltage of a single-cell battery?

Answer 25

1.5 V

Question 26

What does a high resistance indicate about conductance?

Answer 26

Low conductance

Question 27

What type of current is an electric current that periodically changes its direction?

Answer 27

AC (Alternating Current)

Question 28

What is the voltage range for overhead-line systems?

Answer 28

6 kV to 380 kV

Question 29

What is the unit for measuring conductance?

Answer 29

Siemens (S)

Question 30

What are the two kinds of electric voltage?

Answer 30

DC voltage and AC voltage