Electrical Wiring MCQ | Electrical Wiring Questions and Answers

Answer.3. Both 1 and 2

Explanation:-

The subcircuit of the electrical installation feeding supply to various light points, that is lamps, tubes, etc. and to fan points, that is ceiling and table fans, etc. is termed as light and fan sub-circuit, respectively.

1. While planning this circuit for a residential building, the following points must be given proper consideration.
2. The number of light and fan points connected in one sub-circuit should not exceed ten.
3. The total load connected in a sub-circuit should not be more than 800 W.
4. Control of light and fan points in any sub-circuit should be carried out by 5 A switches fitted on a switchboard
5. Socket outlets provided in these sub-circuits should be of a 5 A rating.
6. Only a single-phase supply should be fed to these sub-circuits.

Answer.4. Power sub-circuit

Explanation:-

Power Sub-circuit The part of the complete installation that supplies power to appliances like a hot plate, electric iron, small single-phase motors of washing machine, refrigerator, etc. is generally called the power sub-circuit. The following points must be considered for the proper planning of these circuits.

1. The number of power points connected in one sub-circuit should not exceed two.
2. The load connected to a sub-circuit should not be greater than 3.0 kW.
3. Control of these circuits should be by 15 A switches.
4. Socket outlets provided in these circuits should be of a 15 A rating.
5. These sub-circuits must be used on a single-phase supply.

Answer.2. PVC conduit pipe

Explanation:-

PVC conduit pipe:- Now PVC conduit pipe is mostly in use because this pipe is light in weight, cheaper, and rust-resistant in comparison to iron pipe PVC conduit pipes are available in 15mm, 19mm, 25mm, and 37mm sizes. Its length is generally 3m or 10 ft. This is called a plastic pipe.

Answer.1. Single pole switch

Explanation:-

Single-Pole Switches:-  A single-pole switch is used where it is desired to control a light or group of lights, or other loads, from one switching point. This type of switch is connected in series with the ungrounded (hot) wire feeding the load.

A single-phase supply will have one live (also called line or phase) wire and one neutral wire. The switch is introduced in the live wire. Any appliance can be connected in place of the lamp. When the switch is closed, the full supply voltage is applied across the device and it operates. When the switch is opened the supply is cut off and the lamp gets switched off.

Answer.2. 2 two way switch

Staircase wiring is commonly used for the staircase and corridor lighting. Normally, only a single light lamp is provided in a staircase which is controlled by either of the two switches – one installed at the top and other at the bottom. Similar is the situation in a bathroom common to two rooms The light lamp in the bathroom can be controlled by the switches installed in the two rooms.

Two-way switches have a central terminal. The central terminal of the first switch is connected to the lower position of the second switch, whereas the central terminal of the second is connected to the upper terminal of the first. We can connect the terminal in reverse fashion also i.e Central terminal of the first switch is connected to the upper position of the second switch, whereas the central terminal of the second is connected to the lower terminal of the first. The figure shows a diagram of two-way switching, that is control of light from two different switches (staircase lighting). When the phase is completed the Lamp start to glow.

Suppose you are at the top of the staircase and the light is in switched off condition, you can switch the light on as you go down, then switch it off as you leave.

Answer.4. 3-pole switch

Explanation:-

This type of connection can be used to control a lamp with switches in three different locations. For example, we can have a lamp on the second floor, controlled by switches on the first floor, second floor, and third floor. The connection makes use of three switches: S1 and S3 are two-way switches and S2 is an intermediate switch.

The connections are shown in Fig. S1 and S3 have two positions: 1 and 2. Switch S2 can have two positions: Connect 1-4 and 3-2 or connect 1-2 and 3-4.

It can be seen that the path is completed and the lamp glows. Now the connection can be broken by any one of the following switch operations:

• Switching S1 to position 1
• Switching S2 to positions 1-2 and 3-4
• Switching S3 to position 2

Thus the lamp can be controlled by three switches. This type of connection can be used in corridors and staircases.

Answer.1. Insulation test between earth and wiring

This test is to measure insulation resistance between each conductor and earth. Leakage current is traced by this test hence it is called leakage current test. Leakage current should always be less than 1/5000th part of the total current of in the circuit. This can be calculated by the following formula. Insulation test between earth and wiring.

Leakage current = supply voltage/insulation resistance measured by megger

Answer.3. Polarity test

Explanation:-

Polarity test- This test tells whether all phase wires are controlled by a switch or not.

Steps of polarity test

1. Put the main switch in off position.
2. Take out all the fuses.
3. Put all switches to off position in the circuit.
4. Take out all the lamps and open the wires of fans.
5. Now join one terminal of megger to main switch phase and rewind tunnel to the phase of ant switch
6. Now rotate the megger with 160 rpm. If the needs of megger go up to zero at means phase wire is controlled by the switch. If it goes up to infinity it mains phase wire is not controlled by switches.
7. Similarly, test all the switches.

A polarity test can also be conducted by a Neon tester. If a neon tester glows on touching switch wired it means it is controlled by the switch.

Answer.3. Amperes

An electric fuse is a device used in the household electric wiring that protects appliances from high current. Fuse wire is connected between the mains and leads of the primary circuit of an electric appliance. When the excess amount of electricity passes through the wire, the fuse wire gets heated and the heat produced fuses or melts the wire breaking the power supply to the circuit of the appliance. Thus, the electric appliance is protected from the passage of a high electric current which destroys the appliance.

A fuse rating is a current need to blow the fuse. Fuses are rated in amps and will be placed as close to a power distribution point as possible to minimize runs of unprotected cable.

Generally, the lowest-rated fuse is selected consistent with reliable operation, but for emergency equipment, the highest rating is used consistent with cable protection.

Answer.2. Brown

Explanation:-

Indian standard Wiring Rules.

• The mains supply is delivered to houses using three-core wiring called the live neutral and the earth.
• The live wire is brown in color and brings in the current. the neutral-colored Blue is the return wire. The earth is colored green or yellow.
• These wires supply electricity to separate circuits within the house.
• Two separate circuits are used one of 15A for Appliance with higher power ratings and the other of 5A ratings for others.
• The earth wire is usually connected to a metal plate deep in the earth near the house.