Tag: physics

Questions Related to physics

If a fuse is rated as 8 A, and current more than 8 A passes through it then

physics electric current and its effects electric fuse electrical fuse and mcb fuse

  1. it would melt

  2. circuit gets broken

  3. both

  4. none

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Correct Option: C
Explanation:

The maximum current which can flow through a fuse without melting it is called its rating.for example a fuse rated at 8A,can stand current upto 8 A. If current higher than 8 A flows through the fuse, it would melt and circuit gets broken the rating of a fuse depends upon the thickness of the fuse wire (because length of the wire is fixed). The thicker fuse has higher rating. So, the thickness of the fuse wire in 8 A circuit is more than that of the fuse wire in 5 A circuit.

Material used in fuse wire must have

physics electric current and its effects electric fuse electrical fuse and mcb fuse

  1. high melting point

  2. low melting point

  3. high resistance

  4. none

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Correct Option: B
Explanation:

A fuse is a piece of thin wire of a material having low melting point, high resistance. It is based in heating effect on current.

Fuse wire is made up of

physics electric current and its effects electric fuse electrical fuse and mcb fuse

  1. Alloy

  2. Mixture

  3. Metals

  4. Non metals

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Correct Option: A
Explanation:

Fuse is generally made up of  an alloy of tin and lead. It is used in series with an appliance to prevent it from damage when excessive flows through the appliance. Material to be used in fuse wire must have Low melting point, low boiling point and high electric resistance.

Mark the correct statement about the material to be used in fuse wire.

physics electric current and its effects electric fuse electrical fuse and mcb fuse

  1. Low melting point

  2. Low boiling point

  3. High electric resistance

  4. All

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Correct Option: D
Explanation:

Fuse wire has 

$\rightarrow$ Low melting point
$\rightarrow$ low boiling point
$\rightarrow$ High electric resistance

Mark the correct reason why a fuse is always connected in series

physics electric current and its effects electric fuse electrical fuse and mcb fuse

  1. When fuse melts, it breaks down the entire home circuit and no current flows

  2. In series connection the current for the entire house pass through the fuse

  3. Both

  4. None

Show answer
Correct Option: C
Explanation:

A fuse is always connected in series because 

when fuse melts, it breaks down the entire home circuit and no current flows
$\rightarrow$ In series connection the current for the entire house pass through the fuse 

Which of the following is the function of MCB in household circuit?

physics electric current and its effects electric fuse electrical fuse and mcb fuse

  1. This switches automatically turn off when current exceeds safe limit

  2. This switches automatically turn on when current exceeds safe limit

  3. Saves the electrical appliances from getting damaged due to excess current

  4. Saves from shortcircuiting

Show answer
Correct Option: A,C,D
Explanation:

An MCB functions by interrupting the continuity of electrical flow through the circuit once a fault is detected. In simple terms MCB is a switch which automatically turns off when the current flowing through it passes the maximum allowable limit.

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected.

What is MCB in household circuit connection?

physics electric current and its effects electric fuse electrical fuse and mcb fuse

  1. Micro Circuit Breakers

  2. Miniature Circuit Breakers

  3. Miniature Circuit Builders

  4. Mega Circuit Blockers

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Correct Option: B
Explanation:

An MCB or miniature circuit breaker is an electromagnetic device that embodies complete enclosure in a molded insulating material.

What is/are the advantage of MCB over fuses? 

physics electric current and its effects electric fuse electrical fuse and mcb fuse

  1. Its wire melts unlike fuses wire

  2. It automatically turn off to save from excess electricity

  3. It takes less time to break the circuit as compare to fuse while overloading

  4. None of these

Show answer
Correct Option: B,C
Explanation:
MCB has several advantages over fuse:
  1. MCB is more sensitive to current than the fuse. It detects any abnormality in the current flow and automatically switches off the electrical circuit.
  2. In the case of MCB, the fault zone of the electrical circuit can be easily identified. Faulty circuit trips to the off position. On the other hand in case of the fuse, the complete fuse wire needs to be checked by opening fuse grip for confirming the fault zone.
  3. With MCB it is very simple to resume to the supply. You just need to push the knob of MCB back to on position. But in case of the fuse, the entire fuse wire needs to be replaced.
  4. MCB provides a better interface with the help of knob than a fuse. In case of the fuse, the compete for handle needs to be taken care out.
  5. Handling MCB is electrically safer than handling a fuse.
  6. MCB is reusable and hence has less maintenance and replacement cost. Whereas a fuse needs to be replaced whenever it goes faulty.

Choose the correct option 

physics electric current and its effects electric fuse electrical fuse and mcb fuse

  1. MCB is much more sensitive to over current than fuse

  2. Fuse is much more sensitive to over current than MCB

  3. Handling MCB is more electrically safe than fuse

  4. Handling fuse is more electrically safe than MCB

Show answer
Correct Option: A,C
Explanation:

Nowadays MCB in low voltage electrical network is commonly used instead of fuse. The fuse may not sense the overcurrent but the miniature circuit breaker does it in a more reliable way. MCB is much more sensitive to over current than fuse. Handling a MCB is electrically safer than a fuse.

In electric fuse, some special wire is used, which is having _______ melting point

physics electric current and its effects electric fuse electrical fuse and mcb fuse

  1. low

  2. high

  3. moderate

  4. very high

Show answer
Correct Option: A
Explanation:

Fuse is a piece of a wire of material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wire gets heated up and melts.