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Electrical safety questions for the CSCS MAP test

4 free questions on Electrical safety, from section C. General safety. Every question is original and explains why each option is right or wrong.

Last verified against HSE guidance and the law ·How we write our questions

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Question 1

Medium ·Link to this question (question 1)

A contractor wants to work on a circuit while it is live to "save time".

What does HSE say?

Choose one answer.

  1. A. It is fine for circuits under 230 volts
  2. B. Avoid live work; isolate the circuit first
  3. C. It is fine if the electrician is very experienced
  4. D. It is fine if the electrician wears gloves
Show the answer and explanation

Answer: B

  • A. Wrong: Wrong. 230 volts can kill.
  • B. Right: Right. HSE says safe isolation procedures must be followed. Live work is only allowed in rare, justified cases.
  • C. Wrong: Wrong. Experience doesn't make live work safe.
  • D. Wrong: Wrong. Gloves alone are not a safe system of work.

Explanation

Work on electrical systems should be done dead, after safe isolation, by competent people.

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Question 2

Medium ·Link to this question (question 2)

You are planning the temporary electrical supply for a site.

Which supply voltage does HSE recommend for portable tools?

Choose one answer.

  1. A. 400 volts, so tools are more powerful
  2. B. Any voltage, as long as there is an RCD
  3. C. 110 volts, centre-tapped to earth
  4. D. 230 volts, as it is the same as at home
Show the answer and explanation

Answer: C

  • A. Wrong: Wrong. Higher voltage means greater shock risk.
  • B. Wrong: Wrong. RCDs are a back-up. Reduced voltage is the main control.
  • C. Right: Right. HSE recommends 110 volt centre-tapped to earth supplies on construction sites, as a shock is much less likely to kill.
  • D. Wrong: Wrong. 230 volts is more dangerous on a construction site.

Explanation

Use 110 volt centre-tapped to earth supplies, or battery tools, on site. Use RCDs as a back-up where 230 volts is needed.

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Question 3

Medium ·Link to this question (question 3)

A worker says the RCD on their extension lead means they don't need to check the tool's cable.

What does HSE say?

Choose one answer.

  1. A. RCDs only work on 110 volt supplies
  2. B. An RCD is only a back-up
  3. C. The RCD makes any damage safe
  4. D. RCDs don't need testing
Show the answer and explanation

Answer: B

  • A. Wrong: Wrong. RCDs are used on 230 volt supplies as a back-up.
  • B. Right: Right. HSE says an RCD is a secondary safeguard. Tools, plugs and cables still need checking.
  • C. Wrong: Wrong. A damaged cable can still cause a shock or fire.
  • D. Wrong: Wrong. Test plug-in or socket RCDs with the test button before use.

Explanation

RCDs are a back-up, not a replacement for checking equipment. Test them before use.

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Question 4

Medium ·Link to this question (question 4)

An electrician says a circuit is safe to work on because they switched it off at the light switch.

What should happen?

Choose one answer.

  1. A. Work quickly before anyone turns it back on
  2. B. Ask someone to stand by the switch
  3. C. Isolate it safely and prove it dead
  4. D. Nothing, as a switch makes it safe
Show the answer and explanation

Answer: C

  • A. Wrong: Wrong. That is not a safe system of work.
  • B. Wrong: Wrong. Use proper isolation and locking off.
  • C. Right: Right. HSE says safe isolation procedures must be followed at all times.
  • D. Wrong: Wrong. A light switch doesn't isolate a circuit.

Explanation

Follow safe isolation: isolate, lock off and prove dead before working on a circuit.

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