Elex Gen Questions

Question 1

The unit of current is

Answer 1

Ampere

Question 2

The unit of voltage is

Answer 2

Volt

Question 3

The unit of resistance

Answer 3

Ohm

Question 4

Hertz is the unit of

Answer 4

Frequency

Question 5

The number of significant digits in the number 0.1050 is

Answer 5

Four

Question 6

A neutral atom with an atomic number of three has how many electrons?

Answer 6

3

Question 7

Electron orbits are called

Answer 7

Shells

Question 8

Materials in which current cannot be established are called

Answer 8

Insulators

Question 9

When placed close together, a positively charged material and a negatively charged material will

Answer 9

Attract

Question 10

Potential difference is another term for

Answer 10

Voltage

Question 11

The unit of energy is the

Answer 11

Joule

Question 12

Which one of the following is the byproduct of a hydrogen fuel cell?

Answer 12

Water

Question 13

Which one of the following is generally not a possible condition in an electric circuit?

Answer 13

Current and No Voltage

Question 14

Electrical current is defined as

Answer 14

the rate of flow of free electrons

Question 15

There is no current in a circuit when

Answer 15

There is no source voltage. and the series switch is open

Question 16

The primary purpose of a resistor is to

Answer 16

Limit current

Question 17

Potentiometers and rheostats are types of

Answer 17

Variable Resistors

Question 18

The current in a given circuit is not to exceed 22 A. Which value of fuse is best?

Answer 18

20A #must not be greater than 22A

Question 19

Power can be defined as

Answer 19

the rate at which energy is used

Question 20

When the needle of an analog ohmmeter indicates infinity, the resistor being measured is

Answer 20

open

Question 21

Series connection current

Answer 21

series connection current = same

Question 22

While putting four 1.5 V batteries in a flashlight, you accidentally put one of them in backward. The light will be

Answer 22

Dimmer than normal

Question 23

If you measure all the voltage drops and the source voltage in a series circuit and add them together, taking into consideration the polarities, you will get a result equal to

Answer 23

zero : KVL

Question 24

A series circuit consists of a 4.7 k Ω a 5.6 k Ω, and a 10 k Ω resistor. The resistor that has the most voltage across it is

Answer 24

10k: The highest resistance

Question 25

Dissipates most power

Answer 25

Smallest resistance

Question 26

In a parallel circuit, each resistor has

Answer 26

The same voltage

Question 27

In a four-branch parallel circuit, there are 10 mA of current in each branch. If one of the branches opens, the current in each of the other three branches is

Answer 27

Erroneous: 10mA

Question 28

A complete short develops across one of five parallel resistors on a PC board. The most likely result is

Answer 28

The fuse in the power supply will blow

Question 29

The output voltage of a balanced Wheatstone bridge is

Answer 29

Equal to zero

Question 30

The primary method of analyzing a circuit with two or more voltage sources is usually

Answer 30

Superposition

Question 31

A magnetic field is made up of

Answer 31

Flux lines

Question 32

The direction of a magnetic field is from

Answer 32

North to South

Question 33

The direction of a magnetic field within a the magnet

Answer 33

South to North

Question 34

Reluctance in a magnetic circuit is analogous to

Answer 34

Resistance in an electric circuit

Question 35

The unit of magnetic flux is the

Answer 35

Weber

Question 36

The unit of magnetomotive force is the

Answer 36

Ampere-Turn

Question 37

A unit of magnetic flux density is th

Answer 37

Tesla

Question 38

The electromagnetic activation of a movable shaft is the basis for

Answer 38

Solenoids

Question 39

When there is current through a wire placed in a magnetic field

Answer 39

A force is exerted on the wire

Question 40

A coil of wire is placed in a changing magnetic field. If the number of turns in the coil is increased, the voltage induced across the coil will

Answer 40

Increase

Question 41

If a conductor is moved back and forth at a constant rate in a constant magnetic field, the voltage induced in the conductor will

Answer 41

Reverse Polarity

Question 42

In the crankshaft position sensor in Figure, the induced voltage across the coils is caused by

Answer 42

a tab passing through the magnetic field

Question 43

The purpose of the commutator in a generator or motor is to

Answer 43

change the direction of the current to the rotor as it spins

Question 44

In a motor, back emf serves to

Answer 44

decrease the current in the armature

Question 45

The torque of a motor is proportional to the

Answer 45

amount of flux and armature current

Question 46

The difference between alternating current (ac) and direct current (dc) is

Answer 46

ac changes direction and dc does not

Question 47

During each cycle, a sine wave reaches a peak value

Answer 47

two times (peak negative)

Question 48

A sine wave with a frequency of 12 kHz is changing at a faster rate than a sine wave with a frequency of

Answer 48

must not exceed given (12khz) so 10khz

Question 49

A sine wave with a period of 2 ms is changing at a faster rate than a sine wave with a period of

Answer 49

.0025s : the lower the time the faster

Question 50

The average value of a 10 V peak sine wave over one complete cycle is

Answer 50

0v

Question 51

The average half-cycle value of a sine wave with a 20 V peak is

Answer 51

Vave = 2Vp/pi = 12.74

Question 52

The instantaneous value of a 15 A peak sine wave at a point 32° from its positive-going zero crossing is

Answer 52

15sin32 = 7.949

Question 53

An advantage of a three-phase induction motor is that it

Answer 53

does not require starting windings

Question 54

The difference in the synchronous speed of the stator field and the rotor speed of a motor is called

Answer 54

slip

Question 55

The duty cycle of a square wave

Answer 55

50%

Question 56

The voltage rating of a capacitor is increased b

Answer 56

increasing the plate separation

Question 57

An uncharged capacitor and a resistor are connected in series with a switch and a 12 V battery. At the instant the switch is closed, the voltage across the capacitor is? When fully charged?

Answer 57

0V after closed-switch, 12V after fully charged

Question 58

A sinusoidal voltage is applied across a capacitor. When the frequency of the voltage is increased, the current

Answer 58

Increases: Capacitive Reactance 1/2piFC. I = V/R. So if XC decrease, R will also decrease hence Current increases.

Question 59

A capacitor and a resistor are connected in series to a sine wave generator. The frequency is set so that the capacitive reactance is equal to the resistance and, thus, an equal amount of voltage appears across each component. If the frequency is decreased,

Answer 59

Vc > Vr: Equation is given by Xc = R, if frequency decreases then Xc increases hence, Xc > R.

Question 60

In a series RC circuit, the voltage across the resistance is

Answer 60

In-phase with current

Question 61

In a series RC circuit, the voltage across the capacitor is

Answer 61

lagging the resistor voltage by 90°

Question 62

When R = XC the phase angle is

Answer 62

45°