Tag: electric fuse

Questions Related to electric fuse

A fuse is a short piece of wire of .............. and ................?

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

  1. high resistance, low melting point

  2. high resistance, high melting point

  3. low resistance, low melting point

  4. low resistance, high melting point

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Correct Option: A
Explanation:

A fuse wire has a HIGH resistance & LESS melting point. so that it can protect the electric appliances at home by undergoing melting due to excess heat produced because of high resistance. 

as a result circuit is not  complete so no current flow in it.
fuse wire have high resistance so that it can handle large magnitude of currents and it have low  melting point so that it can easily melt and break the circuit due to flow of accidentally high magnitude of currents.

Fuse has ..... and .....?

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

  1. high resistance, high melting point

  2. high resistance, low melting point

  3. low resistance, high melting point

  4. low resistance, low melting point

Show answer
Correct Option: B
Explanation:

Melting point of a fuse wire is low. So by any chance if high current flows through the circuit, the fuse melts because of heat produced in the circuit beyond a permissible limit. A fuse must have high resistance so as to oppose the current flowing through it beyond a safe limit.

two identical fuses are rated at 10 A , if they are joined

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

  1. in parallel, the combination acts as a fuse of rating 20 A

  2. in parallel, the combination acts as a fuse of rating 5 A

  3. in series , the combination acts as a fuse of rating 10 A

  4. in series, the combination acts as a fuse of rating 20 A

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Correct Option: A

Two identical fuses are rated at $10\space A$. If they are joined

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

  1. in parallel, the combination acts as a fuse of rating $20\space A$

  2. in parallel, the combination acts as a fuse of rating $5\space A$

  3. in series, the combination acts as a fuse of rating $10\space A$

  4. in series, the combination acts as a fuse of rating $20\space A$

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Correct Option: A,C
Explanation:

A fuse is a type of low resistance resistor that acts as a device to provide over-current protection, of either the load or source circuit.
Where several fuses are connected in series, it is desirable to blow (clear) only the fuse (or other over-current device) electrically closest to the fault. Hence, when two fuses are in series the current rating is simply the current rating of each fuse i.e. in series, the combination acts as a fuse of rating 10 A
When two fuses are in parallel the current rating is simply twice the current rating of each fuse, hence, in parallel, the combination acts as a fuse of rating 20 A.

What is immaterial for an electric fuse wire ?

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

  1. Its specific resistance

  2. Its radius

  3. Its length

  4. Current flowing through it

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Correct Option: A

Name the material used for fuse wire :

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

  1. Electric fuse.

  2. Connecting wire.

  3. Filament of an electric bulb.

  4. Heating element of an electric toaster.

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Correct Option: A

What is immaterial for an electric fuse wire

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

  1. Specific resistance of the wire

  2. radius of the wire

  3. length of the wire

  4. current flowing through the wire

Show answer
Correct Option: C

An electric bulb rated 220 V - 100 W will fuse if it consumes 131 W. What voltage fluctuations can it withstand?

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

  1. up to 230 V

  2. up to 241 V

  3. up to 225 V

  4. up to 252 V

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Correct Option: D
Explanation:

We know that: $P = \dfrac{V^{2}}{R}$
Using the fact that the bulb is $220V - 100W$
$ 100 = \dfrac{220^{2}}{R}$

$R = \dfrac{48400}{100} = 484\ ohm$

Given that it will fuse on use of power of $131W$.
Substituting this:
$131 = \dfrac{V^{2}}{484}$

$V^{2} = 131 \times 484 = 63,404$

$\Rightarrow V = 251.8V$   Which is the highest voltage it can experience without fusing.

An 1800 W toaster, a 1.3 kW frying pan are plugged into the same $20 A-120V$ line then

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

  1. fuse will not blow

  2. fuse will blow

  3. supply will spark

  4. fuse is just saved

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Correct Option: B
Explanation:

$I _{toaster}=\dfrac{1800}{120}= 15 A,$


$I _{frying pan}=\dfrac{1300}{120}= 10.83 A$

$I _{net}= 25.83 A > 20 A$ 

because applied current is more than possible value of current which is given in ques. Hence fuse will blow

A fuse wire of radius $0.2$ mm blows out for a current of $5A$. For what current, another fuse wire of same material but of radius $0.3$ mm will blow out?

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

  1. $5$A

  2. $3.2$A

  3. $4.33$A

  4. $11.2$A

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Correct Option: A