ITI Electrician Safety MCQ – Electrician Safety Objective Question & Answer

• The protection provided directly on the equipment itself to avoid electric shock is called  Ground fault detection.
• This safety system detects ground faults, which occur when there is an unintended path for current to flow to the ground.
• When a ground fault is detected, the system automatically disconnects the power supply, reducing the risk of electric shock to users.
• This type of protection is essential for ensuring safety in electrical installations and equipment.

• When a circuit is protected in such a way that there is no potential energy that can cause harm to any person working on it, this condition is referred to as the zero energy state.
• This ensures that the circuit is safe to work on, eliminating the risk of electric shock or other hazards associated with electrical energy.

A zero energy state in a circuit is achieved through several safety practices designed to eliminate any potential energy that could cause harm. Here are the key methods:

1. Disconnect Switch Devices: Properly designed electrical systems should include disconnect switches that allow for the safe isolation of circuits, ensuring that no power is supplied during maintenance or servicing.
2. Temporary Grounding: Grounding wires may be connected to the load being serviced. This provides additional protection by preventing any potential build-up of electrical energy.

Sharp-edged tools should ideally be kept separate and packed in a wooden box. This practice provides several benefits:

1. Safety: Storing sharp tools in a wooden box helps prevent accidental cuts or injuries. The wooden box acts as a protective barrier, reducing the risk of contact with the sharp edges.
2. Protection: A wooden box can protect the tools from damage, moisture, and dust, which can affect their performance and longevity.

• Class C fire extinguishers are specifically designed to extinguish fires that originate from electrical sources.
• They use non-conductive agents, such as carbon dioxide (CO2) or dry chemical powders, which effectively smother the fire without conducting electricity, thus minimizing the risk of electric shock.

• The resistance of wet skin of human body in the range of 1000Ω or 1 KΩ
• Internal Resistance: The internal resistance of the human body is approximately 300Ω under normal conditions.
• The internal resistance is primarily due to tissues and fluids within the body, is significantly lower. Research and various sources suggest a range of 300-1000 Ω as a reasonable approximation.
• External Resistance: The skin, particularly dry skin, offers the highest resistance (can be over 100,000 Ω). While wet skin can reduce this resistance to around 1000Ω or lower.

• The first and most crucial action after someone receives an electric shock is Isolate the power source.
• This is crucial because ensuring that the power source is turned off or disconnected prevents further injury to the victim and allows for safe assessment and treatment.
• Only after confirming the power source is safe can you check if the person is breathing or administer artificial respiration if necessary.

Humans are more vulnerable to electric shock from current at 25 Hz compared to higher frequencies.

Why lower frequency currents are more dangerous for the human body?

• Lower Impedance:

  • The human body’s impedance (resistance to electrical current) decreases at lower frequencies. This means that at 25 Hz, the body offers less resistance to the flow of current, allowing a greater amount of current to pass through.
  • Higher current flow increases the risk of serious effects like ventricular fibrillation (a dangerous heart rhythm) or tissue damage.

• Longer Pulse Duration:

  • Frequency refers to the number of cycles per second of an alternating current (AC). Lower frequency means each cycle takes longer.
  • This longer duration of each pulse of current can have a greater impact on tissues and nerves, increasing the potential for harm.

Dry powder fire extinguishers are versatile and can be used on multiple classes of fires, including:

• Class A: Fires involving flammable solids such as wood, paper, and textiles.
• Class B: Fires involving flammable liquids like petrol, diesel, and paint.
• Class C: Fires involving Electrical Fire.
• Class D: Fires involving combustible metals (specific types of dry powder extinguishers).

• Water is effective for extinguishing fires involving ordinary combustibles (Class A)  such as wood, paper, and textiles because it cools the burning material and removes heat from the fire.
• However, it is important to note that water should not be used on fires involving electrical equipment, flammable gases, or certain combustible substances as it can exacerbate the situation or create additional hazards.

Reverse connection in 3-phase motor is not a cause of fire.

• (a) Wrong fuse rating: Using a fuse with a higher rating than the circuit’s capacity allows excessive current to flow. This can overheat wires and components, leading to insulation damage and potentially starting a fire.

• (b) Loose connections: Loose connections increase resistance at the connection point. This increased resistance generates heat, which can ignite nearby materials.

• (c) Damaged insulation between line and neutral: Damaged insulation creates a path for current to flow between the live (line) and neutral conductors. This can cause a short circuit, generating a large amount of heat and potentially starting a fire.

• (d) Reverse connection in 3-phase motor: Reversing connections in a 3-phase motor will cause the motor to rotate in the opposite direction. It might lead to overheating if the motor is stalled or overloaded due to the reversed rotation, but the reversed connection itself isn’t the primary cause of fire.