Tag: electrical fuse and mcb

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

An electric iron draws a current of 15 A from a 220 V supply. What is the cost of using iron for 30 min everyday for 15 days if the cost of unit (1 unit $=$ 1 k W hr) is 2 rupees?

  1. Rs. 49.5

  2. Rs. 60

  3. Rs. 40

  4. Rs. 10
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$I=15 A, V=220 V, t=30 min$
$Energy=P\times t=VIt$
$=220\times 15\times \frac {30}{60}\times 15$
$=3300\times \frac {1}{2}\times 15 W hr$
$=3.3\times kW\times 7.5 hr$
$=24.75 kW hr$
$Cost=24.75\times 2=Rs. 49.50$

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

The parameter irrelevant for an electric fuse wire is 

  1. its radius.

  2. its specific resistance.

  3. current flowing through it.

  4. its length.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For fuse wire expression for heat produced is given by eq. is  $H = \dfrac{I^2 \rho}{2 \pi ^2r^3}$
Hence, it is independent on length of fuse wire. Thus, the parameter irrelevant for an electric fuse wire is its length.