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Electrical Safety. Flashcards

0
Q
  1. What is conductor ?
A

A material that allows electrons to flow through it.

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1
Q
  1. What is electrical current?
A

It is the flow of electrons through a conductor.

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2
Q
  1. What is an insulator?
A

Insulators resist the flow of electricity.

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3
Q
  1. What is resistance?
A

It opposes electron flow.

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4
Q
  1. What is an electrical circuit?
A

A loop where current flows.

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5
Q
  1. How does current flow in circuit?
A

DC current flows from negative to positive.

AC current flows mostly from hot to neutral.

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6
Q
  1. Parts of a simple AC circuit?
A
  1. Electrical source.
  2. Hot wire that sends electricity.
  3. Consuming device.
  4. Neutral wire that returns electricity.
  5. Earth or ground.
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7
Q
  1. Name of event when something going wrong with a electrical circuit?
A
  1. A faulted circuit.

2. Electrical fault.

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8
Q
  1. What is faulted circuit?
A

In a faulted circuit or electrical fault, current follows the wrong path and bypasses the normal load.

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9
Q
  1. Two ways of a faulted cicuit?
A
  1. The short circuit.

2. The ground fault.

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10
Q
  1. What is short circuit?
A

Two hot wires or a hot wire and a neutral wire touch.

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11
Q
  1. What is ground fault?
A

The hot wire touches an outlet or tool casing.

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12
Q
  1. What does short circuit cause?
A

Shocks and damage equipment. They make excess heat that can start fires. With a short circuit, a tool usually will not work.

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13
Q
  1. What does ground faults cause?
A

Shocks. The outlet or tool may keep working until a person touches it - creating multiple paths to ground.

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14
Q
  1. What are the harmful effects of electricity?
A

Electricity can cause shocks, burns, fires, and explosions in the workplace.

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15
Q
  1. What is the number of leading cause of occupational death in construction for electricity?
A

The fourth.

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16
Q
  1. What can shock cause?
A

Electrocution or it may cause a physical reaction that results in a fall.
Current flowing through your chest, neck, head, or major nerves can stop your breathing.
Current through the heart can make it beat out of rhythm or stop.

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17
Q
  1. What are electric burns?
A

Burns may accompany shock. Resistance to current flow in your body turns into heat. Electricity can cook internal organs or cause internal bleeding. Internal effects may happen days later.

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18
Q
  1. What does cause electrical fires?
A

Heat from electricity can ignite fires.

Bad insulation or loose connections.

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19
Q
  1. What are electrical explosions?
A

They are the fires that burn very fast. Bad insulation, overloaded circuits, or sparking at switch contacts can ignite explosive mixtures in air.

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20
Q
  1. How do we work safely with electricity?
A

At a minimum, employers must follow the OSHA electrical standards (subpart K). This standards provide protection for using temporary wiring in construction.

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21
Q
  1. What are three protective methods the OSHA electrical standards (subpart K)?
A
  1. Electrical isolation.
  2. Grounding.
  3. Circuit interruption.
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22
Q
  1. What is temporary wiring?
A

Electrical wiring installed for a construction project. It must use separate circuits for power and lights. OSHA does not allow power outlets or screw-in converters on light circuits. Power and light circuits must have separate circuit breaker boxes or fuses.

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23
Q
  1. Parts of temporary wiring?
A
  1. Power from portable or vehicle-mounted generators.
  2. Feeder boxes contain the main shut-off switch for site temporary wiring.
  3. The system grounding electrode is located in the main box.
  4. Circuit breaker boxes.
  5. Circuit for power.
  6. Circuit for lights.
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24
Q
  1. What is electrical isolation?
A

We isolate electricity by keeping it away from ourselves or our workplaces.
To isolate electricity we do one or more of the following:
1. Insulate the wires.
2. Isolate the wires in enclosures.
3. Elevate the wires.
4. Bury the wires.
5. Cover the wires.

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25
Q
  1. What is grounding?
A

A separate, low resistance pathway for electricity when it does not follow normal flow from hot to neutral.

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26
Q
  1. How does grounding work?
A

In case of a ground fault, most of the electricity takes the ground to source. This helps keep you from becoming part of the circuit.

27
Q
  1. Where has OSHA extensive requirements for grounding?
A

In 1926.404(f)(1) through (11).

28
Q
  1. Does grounding always work?
A

No. Grounding won’t work if your resistance is less than the ground path. For example:

  1. If you are holding a metal pipe that goes directly to ground.
  2. If you are standing in water.
  3. If your tool doesn’t have a ground connection.
29
Q
  1. What makes a proper ground path?
A

A proper grounding path must do two things:

  1. Prevent electricity from flowing between the enclosure of an electrical circuit or system.
  2. Provide a path for fault current to flow back to its source that is less resistant than other paths.
30
Q
  1. What 4 conditions must the grounding path meet?
A
  1. The path to ground must be permanent and continuous.
  2. The path must have ample capacity to cause the operation of the over current device.
  3. The path must have low resistance.
  4. All circuit parts must be bonded together.
31
Q
  1. The last method of electrical protection required by OSHA subpart K?
A

Circuit interruption.

32
Q
  1. What is circuit interruption?
A

Circuit interrupters break a electrical loop or a circuit, so the electricity does not flow.

33
Q
  1. Two types of circuit interruption?
A
  1. Circuit breakers or fuses for wiring and equipment protection.
  2. Ground fault protection for shock protection.
34
Q
  1. How do circuit breaker and fusesbwork?
A

Circuit breakers or fuses connect in the path of the hot wire. When hot wire flow is over the rating of the circuit breaker or fuse , it opens. This interrupt the circuit before the wire or equipment is damaged.

35
Q
  1. What is the reason for blowing fuses or breakers?
A
  1. Grounding problem.

2. Overload.

36
Q
  1. Who should change the rated capacity of breakers or fuses on a circuit?
A

Only qualified electricians.

37
Q
  1. What are limitations of over current devices?
A

A circuit breaker’s job is to protect equipment from heat build-up caused by overload and faults.
For protection from electrocution, you need Ground Fault Protection.

38
Q
  1. What is ground fault protection?
A

If a short circuit or ground fault happens, electricity should return along the ground path to the source. At the source, this higher rate of current flow opens the circuit breaker or fuse.

39
Q
  1. 2 OSHA alternative mandatory provisions required “in addition to any other requirements for equipment grounding conductors”?
A
  1. GGCI or ground fault circuit interrupter.

2. Assured equipment grounding program.

40
Q
  1. What is a GFCI?
A

GFCI stands for ground fault circuit interrupter. They are installed in the path between the hot and neutral wires of a circuit. The GFCI is not an overcurrent device. A GFCI only cares about the difference in current between the hot and neutral conductors. So a GFCI cannot replace circuit breakers for overcurrent protection. GFCIs are used in combination with - not instead of - fuses or circuit breakers. While circuit breakers and fuses protect wiring and equipment, GFCIs protect you from shock.

41
Q
  1. How does a GFCI work?
A

By detecting differences in current between the hot and neutral wires. If the difference exceeds 5 milliamps, or 5/1,000th of an amp (.005 amp), the GFCI opens the circuit. This difference in current flow is typically well below the threshold of a circuit breaker or fuse. As a result, ground faults-which would never open a circuit breaker will open the GFCI.
For example, if a ground fault directs 6 mA (.006 amp) of current through you, it reduces the current returning to the source on the neutral by the same amount. Because the difference is less than 15 amps, the circuit breaker will not open. But the GFCI will trip because the difference is greater than 5 mA. You are saved from a shock.

42
Q
  1. How do GFCI and circuit breaker shock protection compare?
A

A GFCI opens at 5!milliamps. You might experience a painful shock, if you have dry skin. But you can let go of the wire. So even if your skin is wet or you are standing on a wet surface, the GFCI will open before you experience harmful effects. This flow is well below the threshold for lung paralysis, heart failure, heart paralysis, or burns.
By contrast, a 15 amp fuse or circuit breaker does not open until 15,000 milliamps of power flow through it. This means enough current can flow through you so that you can’t let go of the power.

43
Q
  1. Where are GFCIs installed?
A

On all 120-volt single-phase 15 and 20-amp receptacle outlets used by employees on the construction site - accept outlets which are part of the permanent wiring of the building or structure.
GFCIs are installed almost anywhere anywhere in the electrical circuit:
1. At the service entrance panel.
2. At the branch circuit panel.
3. At the outlet level.
4. On every extension cord used for power delivery.

44
Q
  1. What must an employer who does not use have?
A

An assured equipment grounding program.

45
Q
  1. What is an assured equipment grounding program?
A
  1. Written program.
  2. Competent person(s).
  3. Inspection.
  4. Testing.
  5. Equipment availability.
  6. Record-keeping.
46
Q
  1. What i s written program of assured equipment grounding program?
A

Available for inspection and copying by OSHA or any affected employee.

47
Q
  1. What is competent person(s) of assured equipment grounding program?
A

To do daily inspection and periodic testing.

48
Q
  1. What is inspection of an assured equipment grounding program?
A

Each day before work, inspect for defects:

  1. All cord sets.
  2. Attachment caps.
  3. Plugs and receptacles.
  4. Any equipment connected by cord and plug even if fixed and not exposed.
49
Q
  1. What is testing of an assured equipment grounding program?
A

Continuing testing on all equipment ground conductors before first use, following repairs, and at least every three months.

50
Q
  1. What is equipment availability of an assured equipment grounding program?
A

All equipment is inspected and tested before use.

51
Q
  1. What is record-keeping of an assured equipment grounding program?
A

The employer keeps a record of all test and inspections. The NECA color coding scheme is one way to keep track of inspections.

52
Q
  1. What else does OSHA require accept circuit interruption?
A

Subpart K also includes detailed wiring designs, methods, and installation practices.

53
Q
  1. How do we select an extension cord?
A

For portable power tools and appliances, OSHA permits only 3-wire extension cord sets designed for hard or extra hard usage.

54
Q
  1. Extension cord marking?
A
  1. Wire size.
  2. Number of conductors.
  3. Cord type.
  4. AMP rating.
55
Q
  1. Extension cord types?
A
  1. Hard use: S, ST, SO, STO.

2. Junior hard use: SJ, SJO, SJT, SJTO.

56
Q
  1. Where can’t we use an extension cord?
A
  1. Do not pass through holes in walls, floors, or ceilings or through windows or doors.
  2. Do not run behind building walls, ceilings, or floors.
  3. Do mot attach to building surface (including hanging them from nails, staples or bare wire).
  4. Do not use as a substitute for the fixed wiring of a structure.
57
Q
  1. What is strain relief?
A

When cords are plugged in, a lot of pressure is applied th the prongs or to the connectors. This can loosen the prongs or the connection of the conductors to the prongs. The easiest way to prevent this problem is by using strain relief on the cords.

58
Q
  1. How do we plug or unplug an extension cord?
A

Pull on the plug, not the cord. This prevents stressing the terminals where the conductors connect to the plug.

59
Q
  1. What is the most unforgivable misuse of an extension cord?
A

Removing the ground connection.

60
Q
  1. How do we maintain extension cords?
A

Clean, inspect, coil, and store extension cords. Wipe with a dry reg.

61
Q
  1. How do you coil extension cords?
A

Using a figure 8, regular coil, reverse coil, or winding armature.

62
Q
  1. How do you store extension cords?
A

Away from oil, dirt, solvents, acids, caustics, or moisture. Keep away from sharp tools.

63
Q
  1. How do we inspect extension cords?
A

Visually at least once each day, before use:
Check the insulation for cracks, cuts, or breaks. Look for insulation damage and for bent or weakened conductors. Are connections at the plug ends frayed?
Check the plug attachment. Are male plug ends damaged or bent?
Extension cords should have ground continuity testing at least every 90 days.

64
Q
  1. What about GFCIs on extension cords?
A

With a GFCI extension cord, when defects in isolation or grounding happen, the GFCI can shut down the current in the extension cord before a shock. A GFCI extension cord reduces the possibility of false shutdowns caused by normal current loss in a circuit - as often happens when GFCIs are located father away in outlets or in circuit boxes.

Plumbing (23 decks)

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