Question 1

One application for a series d.c. motor is:
A) an electric train
B) a microwave oven
C) a central heating pump
D) an electric drill.

Accepted Answer

A,D

Question 2

An a.c. series circuit has a capacitive reactance of 12 ? and a resistance of 9 ?. The impedance of this current will be:
A) 3 ?
B) 15 ?
C) 20 ?
D) 108 ?.

Accepted Answer

The impedance of an AC series circuit is given by the formula √((R^2 + XC^2)) where R is the resistance and XC is the capacitive reactance. 
In this case, R = 9 Ω and XC = 12 Ω. 
Therefore, impedance Z =√((9^2 + 12^2)) = √(81 + 144) = 15 Ω. 
Hence, the correct answer is choice B) 15 Ω.

Question 3

An a.c. series circuit has an inductive reactance of 4 ? and a resistance of 3 ?. The impedance of this circuit will be:
A) 5 ?
B) 7 ?
C) 12 ?
D) 25 ?.

Accepted Answer

The impedance $Z$ of an AC series circuit is given by $Z = \sqrt{R^2 + X_L^2}$, where $R$ is the resistance and $X_L$ is the inductive reactance. Substituting $R = 3 \Omega$ and $X_L = 4 \Omega$, we get $Z = \sqrt{3^2 + 4^2} = \sqrt{9 + 16} = \sqrt{25} = 5 \Omega$.

Question 4

A straight line having definite length and direction that represents to scale a quantity such as current voltage or impedance is called:
A) a series a.c. circuit
B) capacitive reactance
C) a phasor, as in a phasor diagram
D) the impedance triangle.

Accepted Answer

A phasor is a vector representation of a sinusoidal waveform, often used in electrical engineering to represent the magnitude and phase of a quantity such as voltage or current in a circuit. It has a definite length and direction, and is often depicted in a phasor diagram. Choices A, B, and D do not accurately describe a phasor.

Question 5

The total opposition to current fl ow in any a.c. circuit is called:
A) resistance
B) inductance
C) reactance
D) impedance.

Accepted Answer

The total opposition to current flow in any AC circuit is called impedance. Impedance includes both resistance and reactance (inductive and capacitive), so choices A, B, and C are all incorrect as they only refer to individual components of impedance.

Question 6

The opposition to current flow in an a.c. capacitive or inductive current is called:
A) resistance
B) inductance
C) reactance
D) impedance.

Accepted Answer

The opposition to current flow in an a.c. capacitive or inductive circuit is called reactance. Reactance is different from resistance, which is the opposition to current flow in a d.c. circuit. Inductance and impedance are related concepts, but do not directly refer to the opposition to current flow in an a.c. circuit.

Question 7

The opposition to current flow in an a.c. resistive circuit is called:
A) resistance
B) inductance
C) reactance
D) impedance.

Accepted Answer

Resistance is the correct term for the opposition to current flow in an AC circuit when only resistive elements are present. Reactance and impedance involve inductive and capacitive elements, which are not specified in the question.

Question 8

Two identical resistors are connected in parallel across a 24 V battery. The voltage drop across each resistor will be:
A) 24 V.
B) 2 V
C) 6 V
D) 12 V

Accepted Answer

When resistors are connected in parallel, the voltage across each resistor is the same as the voltage across the parallel combination, which is 24 V in this case.

Question 9

Two identical resistors are connected in series across a 24 V battery. The voltage drop across each resistor will be:
A) 2 V
B) 6 V
C) 12 V
D) 24 V.

Accepted Answer

When resistors are connected in series, the voltage drop is divided between them proportionally to their resistance. Since both resistors are identical, they have the same resistance and therefore the voltage drop across each resistor will be half of the total voltage drop across the series circuit. So, the voltage drop across each resistor will be 12 V.

Question 10

The inductive reactance of a 100 mH coil when connected to a 50 Hz supply will be:
A) 5 ?
B) 20 ?
C) 31.42 ?
D) 31.42 k?.

Accepted Answer

The formula for inductive reactance is Xl = 2πfL, where Xl is the inductive reactance, f is the frequency, and L is the inductance. 
Plugging in the values, we get Xl = 2π(50)(0.1) = 31.42 Ω. Therefore, the correct answer is C.

Question 11

The capacitive reactance of a 100 ?F capacitor when connected to a 50 Hz supply will be:
A) 5 ?
B) 20 ?
C) 31.8 ?
D) 31.8 k?.

Accepted Answer

The formula for capacitive reactance is Xc = 1/(2πfC), where Xc is the capacitive reactance in ohms, f is the frequency in hertz, and C is the capacitance in farads. Substituting the given values, Xc = 1/(2π*50*0.0001) = 31.8 Ω.

Question 12

A circuit with bad power factor causes:
A) a fall in the supply voltage
B) an increase in the supply voltage
C) more current to be taken from the supply
D) less current to be taken from the supply.

Accepted Answer

A circuit with bad power factor means that the circuit is drawing more current than necessary to power the same load. This increased current causes more current to be taken from the supply.

Question 13

A good insulator material:
A) has lots of free electrons
B) has no free electrons
C) may be made of copper
D) may be made of plastic.

Accepted Answer

A good insulator material has no free electrons, which means it does not conduct electricity.

Question 14

A good conductor material:
A) has lots of free electrons
B) has no free electrons
C) may be made of copper
D) may be made of plastic.

Accepted Answer

The answer of A good conductor material:
A) has lots of...

Question 15

Good insulator materials are:
A) copper
B) PVC
C) brass
D) wood.

Accepted Answer

PVC (Polyvinyl Chloride) is a type of plastic that has high electrical insulation properties, making it a good choice as an insulator material. Copper and brass are conductors and wood can be a conductor or insulator depending on its moisture content.

Question 16

Good conductor materials are:
A) copper
B) PVC
C) brass
D) wood.

Accepted Answer

Copper and brass are both metals known for their excellent conductivity, making them good conductors of electricity. PVC and wood, on the other hand, are insulators.

Question 17

An electromagnetic switch operated by a solenoid is one definition of:
A) a transformer
B) an a.c. motor
C) a relay
D) an inductive coil.

Accepted Answer

An electromagnetic switch operated by a solenoid is a definition of a relay. A relay is an electrically operated switch that uses an electromagnet to mechanically operate its contacts. It is commonly used in control circuits to turn on and off a load with a low-power signal. The other options (A, B, and D) do not accurately describe an electromagnetic switch operated by a solenoid.

Question 18

A step down transformer has 1000 turns on the primary winding and 500 turns on the secondary winding. If the input voltage was 230 V the output voltage will be:
A) 2 V
B) 115 V
C) 200 V
D) 460 V.

Accepted Answer

The turn ratio of primary to secondary of the transformer is 2:1 (since 1000/500 = 2/1). 
Using the transformer turn ratio equation:

Vp/Vs = Np/Ns

where Vp is the primary voltage, Vs is the secondary voltage, Np is the number of turns in the primary winding, and Ns is the number of turns in the secondary winding.

Substituting given values:

230/Vs = 1000/500

Solving for Vs:

Vs = 230 x 500/1000 = 115 V

Therefore, the output voltage will be 115 V.

Question 19

One application for a shaded pole a.c. motor is:
A) an electric train
B) a microwave oven
C) a central heating pump
D) an electric drill.

Accepted Answer

The answer of One application for a shaded pole a.c....

Question 20

One application for an a.c. induction motor is:
A) an electric train
B) a microwave oven
C) a central heating pump
D) an electric drill.

Accepted Answer

The answer of One application for an a.c. induction motor...

Quiz 2: Understand the Fundamental Principles and Requirements of Environmental Technology Systems

One application for a series d.c. motor is:

An a.c. series circuit has a capacitive reactance of 12 ? and a resistance of 9 ?. The impedance of this current will be:

An a.c. series circuit has an inductive reactance of 4 ? and a resistance of 3 ?. The impedance of this circuit will be:

A straight line having definite length and direction that represents to scale a quantity such as current voltage or impedance is called:

The total opposition to current fl ow in any a.c. circuit is called:

The opposition to current flow in an a.c. capacitive or inductive current is called:

The opposition to current flow in an a.c. resistive circuit is called:

Two identical resistors are connected in parallel across a 24 V battery. The voltage drop across each resistor will be:

Two identical resistors are connected in series across a 24 V battery. The voltage drop across each resistor will be:

The inductive reactance of a 100 mH coil when connected to a 50 Hz supply will be:

The capacitive reactance of a 100 ?F capacitor when connected to a 50 Hz supply will be:

A circuit with bad power factor causes:

A good insulator material:

A good conductor material:

Good insulator materials are:

Good conductor materials are:

An electromagnetic switch operated by a solenoid is one definition of:

A step down transformer has 1000 turns on the primary winding and 500 turns on the secondary winding. If the input voltage was 230 V the output voltage will be:

One application for a shaded pole a.c. motor is:

One application for an a.c. induction motor is: