Tag: electric current and its effects

Questions Related to electric current and its effects

What is the problem when a multi-plugs adaptor is used to connect many appliances to the same socket?

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

  1. The current drawn from the mains gets higher and overheating may occur.

  2. The voltage across the live and neutral wires increases and overheating may occur.

  3. The flow of the current will be slowed down and the power to each appliance will be reduced.

  4. The appliances will be damaged due to the higher current that flows through each appliance.

Show answer
Correct Option: A
Explanation:
  • This means much amount of current will be drawn from the socket.
  • If we plug in a washing machine,a hair dryer ,a 1 HP mixer grinder then out socket will simply melt.
  • So by using multi-plugs adapter current drawn increase result in over heating.

What is the reason for the fuse and switch to be located at the live wire?

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

  1. To cut off the current from the appliance.

  2. To cut off the high voltage from the appliance.

  3. To break the circuit when there is a sudden current surge.

  4. To indicate to the user that the wire is Live wire when fuse and switch is seen on it.

Show answer
Correct Option: B
Explanation:

When by short-circuit or any other reason current exceed its nominal value that time fuse breaks the circuit and so cuts off the high voltage from the appliance which prevent it from damage.

Choose the wrong option regarding miniature circuit breaker (MCB)?

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

  1. MCB contains a metal which melts when the current passing through it exceeds a certain value and hence opens the circuit

  2. Quick restoration of an MCB is possible just by switching on the operation when a breakdown occurs due to current overload

  3. MCB switchess off the circuit automatically when the current passing through it exceeds a certain value

  4. None of the above

Show answer
Correct Option: A
Explanation:

In MCB, whenever continuous current flows, the bimetallic strips is heated and deflect by bending. This deflection of bimetallic strips releases the mechanical latch. It causes to open the miniature circuit breakers contact and the MCB turns of thereby stopping he current to flow in the circuit. Hence $A$ is the wrong statement. 

If the current in a circuit rises too high, the fuse wire will ?

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

  1. melts

  2. cold

  3. proivides light

  4. hot

Show answer
Correct Option: A
Explanation:

Fuse wire have high value of resistance so when high magnitude of current flows through it then due to melting point of it it melts by excessive heating. Fuse is used to protect the circuit from any accidental heavy flow of current.

When a fuse is rated 8A, it means :

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

  1. It will not work if current is less than 8A

  2. It has a resistance of 8 ohm

  3. It will work only if current is 8A

  4. It will burn if current exceeds 8A

Show answer
Correct Option: D
Explanation:

The work of fuse wire to protect electric appliances if some particular amount of current that should not be passed through is passed accidentally.


The resistance of fuse wire is set as such if current exceeds from a particular amount heat is produced and and temperature of the fuse wire increases and it reaches to it's melting point and it melts and circuit becomes an open circuit. 

So if a wire is rated 8 A, it means the resistance is set to such a value that if current is exceeded from 8 A value then fuse wire will melt down.

Fuse wire is made of :

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

  1. Platinum

  2. Copper

  3. Aluminium

  4. Alloy in tin and lead

Show answer
Correct Option: D
Explanation:

 Electric fuse wire is a wire which allows only upto a limit of current through it , if a particular amount of value of current is exceeded then it melts down.

so for achieving the melting property the fuse wire is made up of an alloy made of tin  63 % & lead 37 % . which can melt down over low temperatures.

A fuse is used in an electrical appliance :

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

  1. To earth the appliance

  2. To protect the appliance and its cable

  3. To change the efficiency of the applicance

  4. To change the current rating of the applicance

Show answer
Correct Option: B
Explanation:

Fuse is a device used to save the electric current from overheating due to the sudden increase in the current in the circuit.
It protects the device and the user when the electric current is higher than the normal needed by a circuit, it blows up breaking the circuit.
Hence protecting the circuit from an a power overload.

Which of the following is false about fuse ?

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

  1. A fuse controls the current that flows to the appliance.

  2. A fuse increases the resistance in the circuit to minimize the current flow.

  3. A fuse allows high current to flow through the circuit without damaging the appliance.

  4. A fuse protects the wiring and the appliance in the circuit from overheating.

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

A fuse is a type of low resistance resistor that acts as a sacrificial device to provide over current protection, of either the load or source circuit. It just controls the amount of current flowing.
It neither increase the resistance of the circuit nor it allows high current. It doesn't allow high current to pass but that doesn't mean, it protect appliances from heating.

In which of the following situations will a fuse possibly melt?

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

  1. The earth wire is broken

  2. There is a short circuit in the electrical circuit

  3. The fuse is fixed along the neutral wire instead of the live wire

  4. The fuse wire is connected to earth wire

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

A fuse wire may possibly melt when :
(i) the earth wire is broken
(ii) the fuse is fixed along the neutral wire instead of the live wire.
(iii) there is a short circuit in the electrical circuit.

What specifications would you select for the material to make a fuse wire?

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

  1. Greater specific heat, low melting point

  2. Greater specific heat, high melting point

  3. Less specific heat, high melting point

  4. Less specific heat, low melting point

Show answer
Correct Option: D
Explanation:

A fuse wire must be made of a material having less specific heat and low melting point. When the current in electric circuit exceeds a safe, limit, the low value of specific heat results in more increase in temperature and the low value of melting point causes it to melt. It thus saves the electrical appliances from getting damaged.