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An electric iron takes a current of $5 A$ and develops $1.5 \times 1 0^{4} J$ of heat energy in $30 s$ . What will be the resistance of the electronic iron?

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20 Ω

30 Ω

15 Ω

40 Ω

answer is A.

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Detailed Solution

An electric iron takes a current of

5 A

and develops

1.5 \times 1 0^{4} J

of heat energy in

30 s

. The resistance of the electronic iron will be

20 Ω

.
Given that, current

I = 5 A

Heat energy,

H = 1.5 \times 1 0^{4} J

Time

t = 30 s

From Joules Law of heating we have:

H = I^{2} Rt

\Rightarrow R = \frac{H}{I^{2} t}

….(1)
Where

I

is the current,

H

is the heat,

R

is the resistance and

t

is the time.
Put the above values in eq (1).

\Rightarrow

R = \frac{1.5 \times 10^{4}}{5^{2} \times 30^{}}

\Rightarrow R = 20 Ω

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