Question

An electric iron of 1 kW is operated at 220 V. Find which of the following fuses that respectively rated at 1 A,3 A and 5 A can be used in it.

Answer 1

Answer:

1A, 3A

Explanation:

1kw = 1000w

P = V^2/R

R = (220)^2/1000 = 48.4 ohm

i = V/R = 220/48.4 = 4.54 A

Therefore, 5A fuse cannot be used since it will not close the circuit even on maximum current.

Answer 2

The electric iron is rated for the fuse in which the current is 5 A.

Explanation:

It is given that,

Electric power of the electric iron, $P=1\ kW=1000\ W$

Voltage, V = 220 Volts

The electric power of an electrical appliance is given by the below formula as :

$P=V\times I$

$I=\dfrac{P}{V}$

$I=\dfrac{1000\ W}{220\ V}$

I = 4.545 A

or

I = 5 A

So, electric iron is rated for the fuse in which the current is 5 A. Hence, this is the required solution.

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