Components

Question 1

potentiometer

Answer 1

a variable resistor used to divide voltage

Question 2

rheostat

Answer 2

a variable resistor used to control current

Question 3

thermistor

Answer 3

resistance sensor that changes resistance as a function of temperature

Question 4

photoconductive cell

Answer 4

a resistance sensor that changes resistance as a function of light

Question 5

strain gauge

Answer 5

a resistance sensor that changes resistance when force is applied

Question 6

switch

Answer 6

a device used to control the opening or closing of circuits

Question 7

pole

Answer 7

the movable arm of a switch

Question 8

throw

Answer 8

the number of contacts that are affected (either opened or closed) by a single switch action (a single movement of a pole)

Question 9

SPST

Answer 9

single-pole-single-throw switch

Question 10

SPDT

Answer 10

single-pole-double-throw switch

one pole contact connects either of two throw contacts

Question 11

DPST

Answer 11

double-pole-single-throw switch

permits simultaneous opening or closing of two sets of contacts

Question 12

DPDT

Answer 12

double-pole-double-throw switch

provides connection from one set of contacts to either of two other sets

Question 13

NOPB

Answer 13

normally open push-button switch

connection is made between two contacts when the button is depressed, and connection is broken when the button is released

Question 14

NCPB

Answer 14

normally closed push-button switch

connection between the two contacts is broken when the button is depressed

Question 15

rotary switch

Answer 15

a knob is turned to make a connection between one contact and any one of several others

Question 16

the resistance of a wire depends on

Answer 16

1. type of material
2. length of the wire
3. the wire’s cross-sectional area
4. temperature

Question 17

resistance of a wire (formula)

Answer 17

R = (ρl)/A

ρ = resistivity (a constant for each material at a given temperature)

l = length

A = cross-sectional area

Question 18

how to measure current with an ammeter

Answer 18

open the circuit, then insert the meter in the circuit as a series connection, with current in at the negative terminal and out at the positive terminal

Question 19

how to measure voltage with a voltmeter

Answer 19

connect the voltmeter in a parallel connection, across the component for which voltage is to be found

Question 20

power rating of a resistor

Answer 20

the maximum amount of power that a resistor can dissipate without being damaged by excessive heat buildup

determined by physical composition, size, and shape of the resistor

Question 21

surface area of a resistor

Answer 21

surface area = length x circumference

Question 22

regulated power supply

Answer 22

a power supply is regulated if the output is constantly sensed and automatically adjusted if it tries to change because of a change in the line voltage or the load

Question 23

efficiency of a power supply

Answer 23

efficiency = (𝑃out)/(𝑃in)

Question 24

output power (formula)

Answer 24

𝑃out = 𝑃in – 𝑃loss

Question 25

power loss (definition)

Answer 25

energy that is dissipated in a circuit, typically in the form of heat due to the resistance within the components

Question 26

capacity for a battery (units)

Answer 26

ampere-hours (Ah)

Question 27

Ah rating

Answer 27

the length of time a battery can deliver a certain amount of current at the rated voltage

Question 28

loading effect of a voltmeter

Answer 28

if the voltmeter’s internal resistance is not sufficiently greater than the resistance that it is paralleled to, the voltage read is altered by the loading effect of the meter

if the meter resistance is at least ten times greater than the resistance across which it is connected, the loading effect can be neglected (and the measurement error is less than 10%)

Question 29

transducer

Answer 29

a device that senses a change in a physical parameter and converts they change into an electrical quantity such as a change in resistance

Question 30

Wheatstone bridge

Answer 30

an electrical circuit, made of four resistors in a bridge formation, that measures unknown resistance with high accuracy