Home › Board exam reviewer › Tools and test equipment

Tools and test equipment: board exam questions with solutions

On the RME exam under Technical Subjects. Try each question before you open its solution, then practise with fresh numbers below: 1 computed question type on this topic.

Loading the reviewer… (it needs JavaScript)

Build it in the lab

Using a multimeter · Testing diodes and transistors with a meter: the same circuits on a live bench, with meters you can move.

Questions

1. Which instrument is used to measure the insulation resistance of cables and motor windings?

  1. Megohmmeter (insulation resistance tester, "megger")
  2. Clamp ammeter
  3. Wheatstone bridge
  4. Power-factor meter
Show the answer and solution

Answer: A. Megohmmeter (insulation resistance tester, "megger")

A megohmmeter applies a high DC test voltage (e.g. 500 V or 1000 V) and reads resistances in the megohm range.

2. How must an ammeter be connected to measure the current through a load?

  1. In parallel with the load
  2. In series with the load
  3. Across the supply terminals
  4. Between the load and earth
Show the answer and solution

Answer: B. In series with the load

An ammeter has very low resistance and must carry the load current, so it goes in series. Connecting it in parallel would effectively short the supply.

3. A technician clamps a clamp meter around a two-core flexible cord (line and neutral together) feeding a 1 kW heater. What will the meter read?

  1. The full heater current of about 4.3 A
  2. Twice the heater current
  3. About zero, because the equal and opposite currents cancel
  4. About half the heater current
Show the answer and solution

Answer: C. About zero, because the equal and opposite currents cancel

The clamp senses the net magnetic field of all conductors inside the jaw. Line and neutral carry equal, opposite currents, so it reads near zero. Clamp only one conductor.

4. A meter movement has full-scale current 1 mA and internal resistance 100 Ω. What shunt resistance converts it into a 0 to 1 A ammeter?

  1. 100 Ω
  2. 1.0000 Ω
  3. 999 Ω
  4. 0.1001 Ω
Show the answer and solution

Answer: D. 0.1001 Ω

The shunt carries 1 − 0.001 = 0.999 A at the same voltage as the meter (0.001 × 100 = 0.1 V). R_sh = 0.1/0.999 = 0.1001 Ω.

5. The same 1 mA, 100 Ω meter movement is to be used as a 0 to 250 V voltmeter. What series multiplier resistance is required?

  1. 249.9 kΩ
  2. 250.0 kΩ
  3. 2.5 kΩ
  4. 250.1 kΩ
Show the answer and solution

Answer: A. 249.9 kΩ

Total resistance = 250/0.001 = 250 000 Ω. R_s = 250 000 − 100 = 249900 Ω = 249.9 kΩ.

6. Before touching conductors that have been switched off and locked out, what is the correct way to confirm they are dead?

  1. Check that the panel indicator lamp is off
  2. Test the voltage tester on a known live source, test the conductors, then re-test the tester on the known live source
  3. Touch the conductor briefly with the back of the hand
  4. Measure resistance between the conductors with the circuit as found
Show the answer and solution

Answer: B. Test the voltage tester on a known live source, test the conductors, then re-test the tester on the known live source

The live-dead-live check proves the tester worked both before and after the test, so a dead reading can be trusted.

7. A digital multimeter will be used for measurements at the service entrance (origin of the installation) of a building. What is the minimum measurement category it should carry?

  1. CAT I
  2. CAT II
  3. CAT IV
  4. CAT III
Show the answer and solution

Answer: C. CAT IV

IEC 61010 places the origin of the installation (service drop, meter, primary overcurrent device) in CAT IV. CAT III covers distribution inside the building, and CAT II covers plug-connected equipment.

8. In the fall-of-potential method of testing a ground electrode, the potential probe is commonly placed at about what fraction of the distance from the electrode under test to the current probe?

  1. 50%
  2. 25%
  3. 90%
  4. 62%
Show the answer and solution

Answer: D. 62%

Placing the potential probe at about 62% of the electrode-to-current-probe spacing gives a reading close to the true electrode resistance for a hemispherical-electrode approximation.

Worked examples with computed numbers

These numbers are fixed on this page; in practice they change every time.

9. An insulation tester applies 1000 V DC and measures a leakage current of 500 nA. What is the insulation resistance?

  1. 2 GΩ
  2. 500 pΩ
  3. 2 MΩ
  4. 500 µΩ
Show the answer and solution

Answer: A. 2 GΩ

R = V/I = 1000/500 nA = 2 GΩ.

Other topics in the same subjects

DC circuits · AC circuits · Three-phase systems · Transformers · Induction motors · Motors, starters and control circuits · Illumination · Protection: fuses, breakers, relays · RA 7920 and ethics (electrical)

An independent, free reviewer: not affiliated with the PRC or the Boards. Subject weights and passing rules are from the PRC examination programs and the laws (RA 9292, RA 7920); check the current PRC program before you file. Code questions follow the Philippine Electrical Code 2017 Part 1; check them against your own copy of the Code.