Electrician Interview Questions

  • What is the difference between Fuse and Breaker?

A fuse contains a wire that melts when exposed to the heat of a short circuit or high current, therefore interrupting the circuit. You must replace it once it has melted.

A circuit breaker cuts off the current without melting (for example, a pair of metal sheets having differing thermal expansion coefficients) and can be reset.

  • What is a Circuit?

Connections to the incoming wires are made inside the panel. These connections are then used to provide power to specific areas of the house.

  • What is CSA approval?

Before an electrical equipment or component can be sold in Canada, it must be certified by the Canadian Standards Association (or a recognised equivalent). This implies that all wiring must be completed with CSA-approved materials. They conduct testing similar to UL (though more stringent), but CSA (or recognised equivalent) clearance is required by law.

  • What about Solar Energy?

Solar panels can be installed on your property by an electrical professional. Your solar panels’ excess energy is channelled into the electricity grid. On your electricity account, you receive credit for power created.

  • What is a Safety Switch?

In the event of a major power leak or surge, a safety switch attached to the property supply shuts off electricity very immediately.

  • What is the NEC?

NEC stands for National Electrical Code. Refer to our page on the NEC for more details.

  • How does electric traction work?

Traction refers to the use of electric power for traction systems, such as trolleys, trams, and railroads. Electric traction all refers to the use of electricity. Today’s bullet trains also use magnetic traction. Basically, electric traction systems use dc motors.

  • What is an encoder and how does it work?

An encoder is a device that converts a signal or data into a code, like a bitstream. The code may be used for a variety of things, including compressing data for storage or transmission, encrypting the input code, adding redundancies, or translating between different codes. When any component is digital, this is often accomplished using a pre-programmed algorithm, whereas analogue encoding is typically accomplished using analogue circuitry.

  • What is a motor’s operation?

Torque is the term for the turning or twisting motion that is produced whenever a current-carrying conductor is placed in a magnetic field.

  • What happens if we supply a bulb or tube light with a 220-volt direct current supply?

Since bulbs are made to run on AC, the AC supply has a high impedance. They typically have little resistance. Low resistance causes the current through a lamp to be so high when a DC supply is supplied that it could harm the bulb.

  • Describe ACSR cable.

Aluminium conductor steel reinforced, or ACSR, is the name of the conductor used in transmission and distribution.

  • In case of a D.C shunt motor under no load condition the air gap flux

In shunt motor,

Ish = V / Rsh.

If V is constant Ish will also be a constant. Hence the flux is constant

  • A moving coil ammeter with a coil with resistance of 1000 ohms has a full-scale deflection of 50. To increase the range to 1 A, the shunt resistance must be _ ohms.


  • What is the difference between capacitance and inductance?

Capacitance: Capacitance is defined as the amount of charge stored inside a capacitor at a fixed voltage.

Inductance is a coil’s ability to resist changes in the electric current running through it. Mutual inductance occurs when the current change in the primary coil is opposed by a secondary coil.

  • What happens when two positively charged elements are combined?

Positives repel and opposites attract. When two positively charged elements are placed next to each other, they repel and move away from each other.

  • What’s the difference between a capacitor, a resistor, and an inductor?

Capacitor: A capacitor is an electrical component that serves as a passive element by opposing current flow. When a potential is applied, it also stores some type of electrical charge.

Resistor:  A resistor is an electrical component that obstructs the flow of current. It is a two-terminal component that is mostly used to minimise current flow.

Inductor: An inductor is an electrical component that stores energy in the form of a magnetic field and is used to build electrical circuits. It is also known as a choke or a coil.

  • What is a two-phase motor?

A two-phase motor is one that features a phase split between the starting and running windings.

  • What exactly is armature reaction?

The reaction of armature flu to main flux is known as armature reaction. The armature flux can either assist or oppose the main flux.

  • What is a circuit breaker?

A circuit breaker is a device that may break a circuit manually or automatically under all conditions, including no load, full load, and short circuit.

  • Name the types of circuit breakers?
  1. AC Circuit Breaker
  2. DC Circuit Breaker.
  • What is ELCB?

ELCB is an abbreviation for Earth Leakage Circuit Breaker. They serve the same purpose as RCCBs but are voltage sensor devices.

  • What is MCB?

Miniature Circuit Breakers are abbreviated as MCBs. The MCB is an electromechanical device that immediately shuts down the circuit whenever an irregularity is detected.

  • What is MCCB?

MCCB stands for Molded Case Circuit Breaker. The MCCB is a device that protects the circuit against overloading. It also includes a manually operated switch for tripping the circuit.

  • What is RCCB?

RCCB is an abbreviation for Residual Current Circuit Breaker. This residual current device is essentially an electrical wiring device that disconnects the circuit anytime current leaks through the human body or current is not balanced between the phase conductors.

  • What exactly is RCD?

An RCD, or residual current device, is a life-saving mechanism that prevents you from receiving a deadly electric shock if you come into contact with something live, such as a bare wire. It can also help to protect against electrical fires.

  • What do you mean by reversal polarity?

Reverse polarity happens when the wires are not properly connected. For instance, suppose the white wire is connected to the hot side and the black wire is connected to the neutral side.

  • How can you reduce reverse polarity?

You can resolve reverse polarity issue by inspecting the wire connection from the outlet or the receptacle. By exchanging this entanglement, you can solve the reverse polarity.

  • What are the different coloured wires in the electric circuit used for?

The various sorts of coloured wires in an electric circuit define the various duties they perform. In the electric circuit, there are seven different sorts of coloured wires that each serve a specific purpose.

Black wire: The black cable is the primary power supply source in the electric circuit. This is not applicable to ground wires. It is used in either the hot or living state.

Green wire: This wire connects to the ground terminal. Green wires can be found in an outlet box.

Red wire: The second principal wire is the red wire. It is used to relay the wire’s live state. It can be utilised in various types of linkages and is present in a 220-volt circuit. Furthermore, it can be connected to either another red or a black wire.

White/Gray: The neutral wire is white or grey. It transports the unbalanced load to the terminal. This wire’s terminus is placed in the ground. This wire can connect to other wires of the same type.

Blue/Yellow: Power is carried by the blue or yellow wires; hence they are used as live wires. In general, most gadgets lack these wires.

  • What are the transistors made of?

The transistors are made of several combinations of n-type and p-type semiconductors.

  • What are tools used needed to measure various electrical parameters in an electrical circuit?

Following is the list of some measuring tools used for the measurement of electrical parameters:

  1. Voltmeter
  2. Ammeter
  3. Ohmmeter
  4. Multi-meter
  5. Power meter
  6. Microwave meter
  7. Cathode Ray Oscilloscope
  8. Signal Generators and Analysers
  9. Wattmeter
  10. Sweep Generator etc.
  • Define Multimeter?

A Multimeter is an electronic device used to test circuit resistance, amps, and voltage. Engineers can test voltage, resistance, and electrical current levels with mustimeters by connecting two leads to various electrical system components.

  • What is a short circuit?

When two or more wires supplying electrical power to the device come into contact with each other, current flows in an unanticipated channel.

In other terms, a short circuit occurs when the phase and neutral wires come into direct contact with each other without any load attached between them.

  • what is NO and NC contact?

 NC means normally-closed contact. NO means normally-open contact.

  • How does NC contact work?

A NC contact, also known as a normally closed contact, performs the same purpose as a NO contact. It remains closed unless a specified criteria is met. An illustration of limit switch operation in this case. When the actuator of a limit switch is pressed, its NC contact, which is used in a circuit, interrupts the circuit or current flow. Similarly, until the coil of a relay is activated, its contacts are permanently closed.

  • How does NO contact work?

A NO contact or a normally open contact is one that remains open until a specified criteria is met. As an example, consider a limit switch. At least one NO contact must be present in a limit switch. The NO contact of the limit switch remains open until the actuator is depressed. When the actuator is depressed, the contact closes and conducts. When it comes to proximity switches, NO contacts remain open until they detect an interruption, whereas pressure switches remain open until the predetermined pressure threshold is exceeded.

  • Define Corona Discharge?

Corona Discharge (or the Corona Effect) is an electrical discharge caused by the ionisation of a fluid around an electrically charged conductor, such as air. The corona effect will occur in high-voltage systems unless care is taken to limit the strength of the surrounding electric field.

  • What exactly is HVAC?

HVAC is an abbreviation for heating, ventilation, and air conditioning. Even the refrigeration “R” is sometimes used, resulting in “HVACR.” HVAC is used to adjust the environment of a limited indoor space based on the needs of the people or items in it.

  • Define earthing?

Earthing is the process of delivering an immediate discharge of electricity to the earth via low resistance wires. The earth electrode connects to the overall mass of the earth. The metallic bodies of all electrical apparatus will be connected to the earth by a low resistivity wire, the neutral point of the supply system or the non-current carrying part of the electrical apparatus will be connected to earth, and the advantage is that there will be no danger if an immediate discharge of electrical energy occurs. If a gadget is electrically connected to an earth electrode, it is said to be earthed.

  • What is a solidly earthed system?

A device or system is considered to be solidly earthed if it is electrically interconnected to a ground electrode with no intention of adding resistance or impedance to the earth connection, and this system can protect the device against over voltages.

  • Define High Rupturing Capacity (HRC) fuse?

The HRC fuse functions similarly to a regular fuse in that the fuse wire can only carry a certain amount of short circuit current. If the flow rate exceeds this, it will burn. HRC fuses are made from glass or some type of chemical component.

  • Define Neutral?

A point with zero potential is referred to as “neutral.” Because each single-phase load necessitates the current return channel, the ideal ground point is referred to as Neutral. The electron should go from source to load to source to ensure a continuous flow. As a result, a faultless return path is required. When you use ground or the earth as a current return path, some resistance is always added to the load, resulting in a voltage drop across the ground. Because of the ground resistance, the exact output from the source cannot be obtained. As a result, the perfect ground point from the source is produced, known as neutral.

  • What is Earthing?

Earthing is a method of avoiding electric shocks. It achieves this by acting as a protective conductor, allowing a fault current to pass to ground. It also causes the protection device, either a circuit breaker or a fuse, to cut power to the faulty circuit.

  • Define Grounding?

Grounding of an electrical system refers to the connecting of current carrying parts to ground, i.e., the connection of power system neutral to ground. Grounding is done to keep the equipment safe.

  • What is DOL Starter?

A Direct On-Line starter, often known as a DOL starter, is a technique of starting a three-phase induction motor. A three-phase induction motor is linked directly across its three-phase supply in a DOL starter, and the DOL starter applies the full line voltage to the motor terminals.

  • What is an induction motor (or asynchronous motor)?

A three-phase induction motor is a single-phase alternating current unit. Only the stator receives a three-phase alternating current source. The rotor receives no power.

  • Define synchronous motor?

The synchronous motor rotor normally rotates at a consistent speed as the machine’s rotating field.

  • Name the types of synchronous motor?

Non-Excited Synchronous Motors

Direct Current (DC) Excited Synchronous Motors.

  • What is magnetic circuit?

The closed path for magnetic flux is called a Magnetic Circuit

  • What is a transistor?

The transistor is an active component and a semiconductor device that is used as an amplifier to magnify high- and low-level signals. It is also used in oscillators, detectors, modulators, and as an electrically controlled switch in digital circuits. In other terms, a transistor is a small version of a device that can be used to regulate or restrict the flow of electronic impulses.

  • Name the major components in a motor control center?
  1. Bus Bar
  2. Circuit Breaker
  3. Magnetic Contactor
  4. Contactor Auxiliary Contact
  5. Relay Control
  6. Control Transformer
  • Define transient in a power system?

Transients are disturbances that affect power quality and are hazardous to the equipment in a power system. The electrical transients would last only a few milliseconds and may be regarded as a short spike. This failure would only last a few milliseconds, but it would be sufficient to transmit a significant quantity of electricity to the power system.