Tag: electrical fuse and mcb

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

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

  1. high resistance, low melting point

  2. high resistance, high melting point

  3. low resistance, low melting point

  4. low resistance, high melting point
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  1. high resistance, high melting point

  2. high resistance, low melting point

  3. low resistance, high melting point

  4. low resistance, low melting point
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When two identical fuses are joined in parallel, the total current capacity is the sum of the individual ratings because the current splits between them. Thus, 10 A + 10 A = 20 A.

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

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

  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 $20\space A$
Reveal answer Fill a bubble to check yourself
A,C Correct answer
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.

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

What is immaterial for an electric fuse wire ?

  1. Its specific resistance

  2. Its radius

  3. Its length

  4. Current flowing through it
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The properties of a fuse wire that determine its melting behavior and resistance to current are its specific resistance, radius, and the current flowing through it. Its length does not affect the heat generated per unit volume or the current rating in a way that matters for typical fuse protection, making length immaterial.

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

What is immaterial for an electric fuse wire

  1. Specific resistance of the wire

  2. radius of the wire

  3. length of the wire

  4. current flowing through the wire
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The heating effect of a fuse wire is primarily determined by its resistance, which depends on its radius and material. The length is generally considered immaterial in basic fuse physics problems.

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

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

  1. up to 230 V

  2. up to 241 V

  3. up to 225 V

  4. up to 252 V
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

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

  1. fuse will not blow

  2. fuse will blow

  3. supply will spark

  4. fuse is just saved
Reveal answer Fill a bubble to check yourself
B Correct answer
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