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A circuit breaker is an electrical switch that protects an electrical circuit from damage caused by overcurrent. It interrupts the flow of current to protect appliances to prevent them from getting damaged.
The advantages of circuit breakers are
- It prevents the excessive flow of current to protect the circuit.
- It is in a form of a switch and can be reset anytime.
- They are reliable.
There are mainly four types of Circuit breakers:
- Vacuum Circuit Breaker
- Air Circuit Breaker
- SF6 Circuit Breaker
- Oil Circuit Breaker
A fuse contains a thin metal wire that melts whenever there is a flow of a large amount of current. It can be used only once. While a circuit breaker can be used many times.
Very Short Answers Questions [1 Mark Questions]
Ques. Which are the contact materials in the vacuum circuit breakers?
Ans. The contact materials used in the vacuum circuit breakers are silver-lead copper-tellurium, silver-bismuth, copper-lead, and copper-bismuth materials.
Ques. What is a circuit breaker?
Ans. A circuit breaker is a device that protects an electrical circuit from damage caused by overcurrent. The basic function of a circuit breaker is to stop the flow of current to protect appliances connected to it and to prevent the risk of fire and damage.
Ques. What is a fuse?
Ans. A fuse is a thin metal wire device that protects the circuit from a heavy flow of electric current through the circuit. The thin wire of the fuse melts whenever there is a flow of a large amount of current. It can be used only once.
Ques. What is the abbreviation of OCPD with respect to circuit breakers?
- Overrating Protective Device
- Overcurrent Protection Device
- Outlook Protection Device
- Overcurrent Protection Disk
Ans. The correct answer is b. Overcurrent Protection Device
Explanation: OCPD protects an electrical circuit against explosive ignition and flash hazards from high voltage and current. The abbreviation of OCPD is Overcurrent Protection Device.
Ques. Give three examples of Overcurrent Protection Devices.
Ans. The following are the three examples of overcurrent protection devices
- Fuses
- Circuit breakers
- Overcurrent relays
Short Answers Questions [2 Marks Questions]
Ques. What is a residual current circuit breaker?
Ans. A residual current circuit breaker (RCCB) is a current-sensing device that can automatically measure the current and disconnected the circuit whenever there is fault occurred in the connected circuit or if the current exceeded the rated sensitivity.
Ques. What is an electrical circuit?
Ans. An electrical circuit is a closed path of electric current that consists of components like resistors, capacitors, diodes, etc. connected by wire in which the current flows.
Ques. What is the common function of both fuse and circuit breakers?
Ans. The common function of a fuse and circuit breaker is to prevent the excess flow of the current through the circuit to protect the appliances from getting damaged connected to it.
Ques. How is the circuit breaker classified according to the operating mechanism?
Ans. According to the operating mechanism a circuit breaker is classified as
- Spring-operated circuit breaker
- Hydraulic circuit breaker
- Pneumatic circuit breaker
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Long Answers Questions [3 Marks Questions]
Ques. What are the functions of MCB?
Ans. The functions of MCB (Miniature Circuit Breaker) are
- It protects the circuit or devices connected to MCB from excessive current.
- If there is any short circuit, it is automatically switched off preventing the damage of the circuit.
- Due to its small size, it is easy to install, maintain, and replace it.
- It gives protection against earth faults provided that the earth fault loop impedance is low enough
- In the domestic installation, they are widely used in place of fuses.
Ques. What is the purpose of a ground fault circuit interrupter (GFCI)?
Ans. The purpose of a ground fault circuit interrupter (GFCI) is to protect a person from electrical shocks that are caused by ground faults.
A ground fault occurs when electric current flows through a person's body instead of flowing through the circuit.
It is designed to detect such ground faults and continuously monitor the current flowing through the circuit by comparing the current in the hot wire with the current in the neutral wire. If there is any difference between these two currents then the GFCI detects a leak in the current and switched off the power supply.
Ques. How do circuit breakers work?
Ans. The choice of a circuit breaker is depend on the types of applications used. The cable and appliances provide resistance to the flow of current through it. Due to any reason if excessive current flows through the circuit, then it will overheat the wires and appliances of the circuit which cause damage to these. A circuit breaker recognizes this heavy current flow and instantly breaks the flow of electricity to stop harm.
Very Long Answers Questions [5 Marks Questions]
Ques. What is the difference between a single-pole and double-pole circuit breaker?
Ans. The differences between a single-pole and double-pole circuit breaker are
| Single-pole circuit breaker | Double-pole circuit breaker |
|---|---|
| It provides 120 volts, 15-20 amps, and has one hot wire and one neutral wire. | It provides 240 volts, 20-60 amps, and has two hot wires that share one neutral wire. |
| It is used with low-voltage appliances | It is used with high-voltage appliances |
| It can control only one hot wire of the circuit. | It can control two hot wires of the circuit. |
| It is used in appliances that require low voltage such as fans, curling iron, TVs, DVD players, and general lighting outlets. | It is used in appliances that require high voltage such as electric dryers, water heaters, and air conditioners. |
Ques. What is the difference between a fuse and a circuit breaker?
Ans. The differences between a fuse and a circuit breaker are
| Fuse | Circuit Breaker |
|---|---|
| A fuse is a thin wire or a metal strip that melts whenever there is a high current flowing through the circuit device. | A circuit breaker uses a switch to disconnect the circuit whenever there is a high current flowing through the circuit. |
| It can be used only once | It can be used many times |
| It provided protection against power overloads | It provides protection against power overloads and short circuits |
| It has a low breaking capacity as compared to a circuit breaker | It has a high breaking capacity as compared to a fuse. |
Ques. What are the advantages and disadvantages of circuit breakers?
Ans. The advantages of circuit breakers are
- It protects the electrical circuit from damage caused by the flow of overrated current.
- It can be reset.
- It is very sensitive in operations
- It is more reliable.
The disadvantages of circuit breakers are
- The installation and repair are costly as compared to the fuse.
- The circuit breaker reacts slower as compared to a fuse.
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