ELECTRICAL COMPREHENSION TESTS

For any Electrical Comprehension test, it is important that you have grasped the basics of electrical understandings. You need to be able to demonstrate good understandings in relation to electrical circuits, electrical elements, functionality and significance.

Within any basic electrical assessment, you most likely come across the following types of questions:

Jobs that often require candidate’s to sit an Electrical Comprehension test are as follows:

• Circuits;
• Electrical Symbols;
• Series and Parallel Circuits;
• Alternating and Direct Currents;
• Voltages;
• Resistance;
• Resistors;
• Diodes.

Before moving on to the advanced section, you should brush up on your physics and electrical knowledge to ensure yourself with the best practice.

QUESTION 1 

What are the basic particles that make up an atom?

A – Protons, neutrons and particles.

B – Protons and electrons.

C – Neutrons, protons and electrons.

D – Mesons, neutrons and electrons.

How to work out the question

Step 1 = this question requires prior knowledge regarding atoms and particles.

Step 2 = that is why it is important to research and revise basic electrical concepts.

Answer

C – Neutrons, protons and electrons.

QUESTION 2 

In the following circuit, if switch A closes, and switch B remains open, what will happen?

A – Bulbs X, Y, and Z will illuminate.

B – Bulb X will illuminate only.

C – Bulbs Y and Z will illuminate.

D – No bulbs will illuminate.

How to work it out

Step 1 = you need to understand how electrical circuits, and what happens to the electrical circuit if something changes i.e. if a switch turns on or off.

Step 2 = if switch A closed, and switch B remains open, no bulbs would illuminate. Even with switch A being an ‘on-switch’, the fact that switch B remains open means that the power supply (i.e. the battery) cannot supply the power because the circuit is broken.

Answer

D – no bulbs will illuminate

QUESTION 3 

In the following circuit, if bulb 3 is removed and the switch is closed, which bulbs will illuminate?

A –Bulb 4 will illuminate.

B – Bulbs 1, 2 and 4 will illuminate.

C – Bulbs 2 and 4 will illuminate.

D – Bulbs 1 and 2 will illuminate.

E – No bulbs will illuminate.

How to work it out

Step 1 = y if the switch is closed, and bulb 3 is removed from the circuit, that means only bulbs 1 and 2 will illuminate.

Step 2 = Bulb 4 will not illuminate because the removal of bulb 3 breaks the path of wiring and therefore prevents bulb 4 from lighting up.

Step 3 =the removal of bulb 3 is on a different path to bulbs and 1 and 2, and therefore does not affect them from illuminating.

Answer

D – bulbs 1 and 2 will illuminate

Depending on the type of job you are applying for, will depend on the complexity of the Electrical test. If you are applying for a high-tech position, it is more than likely that the questions you will be answering in your assessment will be of a complex nature.

Types of questions that you are likely to encounter are as follows:

• Series and Parallel Circuits;
• Transformers;
• Monitoring and Measuring Alternating and Direct Currents;
• Voltages;
• Tolerable Resistances;
• Impedances;
• Magnetic Fields;
• Wheatstone Bridge circuit;
• Earth-Fault Loops;
• Eddy Currents;
• Potential Difference;
• Capacitances;
• Residual current device (RCM);
• Resistors;
• Diodes.

Please note, the above list is not exhaustive. Your assessment will contain questions that are relevant to the job you are applying for, therefore we have provided a general overview of the typical questions found on an Electrical assessment

QUESTION 1 

What are the minimum and maximum acceptable values if a resistor has the resistance of 14 kΩ and can tolerate ±20%?

Minimum value =

Maximum value =

How to work it out

Step 1 = 14,000 ÷ 100 x 20 = 2,800.

Step 2 = Minimum = 14,000 – 2,800 = 11,200 Ω, or 11.2 kΩ

Step 3 = Maximum = 14,000 + 2,800 = 16,800 Ω or 16.8 kΩ

Answer

Minimum = 11.2 kΩ

Maximum = 16.8 kΩ

QUESTION 2 

John turns on his electrical heater. The electrical heater uses a supply of 310 voltages, and the current is 11 A. John wants to work out the resistance of his electrical heater. Calculate the resistance of the electrical heater. Rounded to two decimal places.

How to work it out

Step 1 = n order to work out the resistance, you would need to use the following equation: Resistance = voltage ÷ current = 310 ÷ 11 = 12.1818. To two decimal places = 12.18 ohms.

Answer

12.18 Ω

QUESTION 3 

Using the below Wheatstone bridge circuit, calculate the resistance of R3.

How to work it out

Step 1 = in order to work out the resistance, you should use the following equation:

R1 ÷ R2 = R3 ÷ R4

Step 2 = R1 and R2 = 180 ÷ 400 = 0.45. So, R3 ÷ R4 needs to be equivalent to 0.45

Step 3 = R3 = (180 x 600) ÷ 400 = 270

Step 4 = you can double check to make sure that you have the correct answer by doing the following:

180 ÷ 400 = 0.45.

270 ÷ 600 = 0.45.

Answer

R3 = 270 Ω