Part-66 Module 3 practice test

Question 1

In which direction does electron flow take place in an external circuit?

Accepted Answer

From the negative terminal to the positive terminal

Answer

From the positive terminal to the negative terminal

Answer

In both directions at once

Question 2

One ampere is a flow of:

Accepted Answer

One coulomb per second

Answer

One volt per ohm per second

Answer

One joule per coulomb

Question 3

What is the main difference between a primary cell and a secondary cell?

Accepted Answer

A secondary cell can be recharged; a primary cell cannot

Answer

A primary cell can be recharged; a secondary cell cannot

Answer

A primary cell gives AC; a secondary cell gives DC

Question 4

Which device produces a voltage when two dissimilar metals joined together are heated?

Accepted Answer

A thermocouple

Answer

A piezoelectric crystal

Answer

A photocell

Question 5

A 24 V motor draws 10 A. What power does it take from the supply?

Accepted Answer

240 W

Answer

2.4 W

Answer

34 W

Question 6

A 28 V supply feeds two parallel branches of 7 Ω and 14 Ω. What is the total current?

Accepted Answer

6 A

Answer

1.3 A

Answer

2 A

Question 7

How does the resistance of a conductor change if its length is doubled?

Accepted Answer

It doubles

Answer

It halves

Answer

It stays the same

Question 8

Resistors of 10 Ω, 20 Ω and 30 Ω are connected in series. What is the total resistance?

Accepted Answer

60 Ω

Answer

5.5 Ω

Answer

20 Ω

Question 9

What happens when two north poles of magnets are brought together?

Accepted Answer

They repel

Answer

They attract

Answer

Nothing

Question 10

To what percentage of the supply voltage does a capacitor charge in one time constant?

Accepted Answer

About 63%

Answer

About 37%

Answer

100%

Question 11

Capacitors of 10 µF and 20 µF are connected in parallel. What is the total capacitance?

Accepted Answer

30 µF

Answer

6.7 µF

Answer

15 µF

Question 12

What is the unit of capacitance?

Accepted Answer

The farad

Answer

The henry

Answer

The coulomb

Question 13

What is the function of the commutator in a DC generator?

Accepted Answer

To convert the armature's AC into DC at the brushes

Answer

To produce the main magnetic field

Answer

To regulate the output voltage

Question 14

Which type of DC motor gives the highest starting torque and is used for engine starters?

Accepted Answer

Series-wound

Answer

Shunt-wound

Answer

Permanent magnet with no field winding

Question 15

Why do many aircraft use 400 Hz AC rather than 50 or 60 Hz?

Accepted Answer

Smaller, lighter transformers and motors

Answer

400 Hz cannot cause electric shock

Answer

400 Hz has lower cable losses

Question 16

How many degrees apart are the phases of a three-phase supply?

Accepted Answer

120°

Answer

90°

Answer

180°

Question 17

In a purely inductive circuit, how does the current relate to the voltage?

Accepted Answer

The current lags the voltage by 90°

Answer

The current leads the voltage by 90°

Answer

They are in phase

Question 18

A series circuit has a resistance of 30 Ω and a reactance of 40 Ω. What is the impedance?

Accepted Answer

50 Ω

Answer

70 Ω

Answer

10 Ω

Question 19

What is the synchronous speed of a 4-pole induction motor on a 400 Hz supply?

Accepted Answer

12,000 rpm

Answer

6,000 rpm

Answer

1,600 rpm

Question 20

An alternator has 8 poles and runs at 6,000 rpm. What frequency does it produce?

Accepted Answer

400 Hz

Answer

800 Hz

Answer

50 Hz