એક ઇલેક્ટ્રિક હિટર દ્વારા આપેલા જથ્થાનું પાણી 5 મિનિટમાં ઊકળવા લાગે છે. જો આ હિટરને લાગુ પાડવામાં આવતો સપ્લાય વોલ્ટેજ અડધો કરવામાં આવે તો આટલા જ જથ્થાનું પાણી______ મિનિટમાં ઊકળશે. (હિટરનો અવરોધ અચળ રહે છે તેમ લો.)

A 40
B 20
C 10
D 2.5

Verified Solution

Answer & Solution

Correct Answer

(B) 20

Step-by-step Solution

Detailed explanation

(B)
ઉત્પન્વ થતી ઉખ્મા \(H =\frac{ V ^2}{ R } t\)
\(\begin{aligned} & \therefore & H _1 & = H _2 \\ & \therefore & \frac{V_1^2}{ R } t_1 & =\frac{ V _2^2}{ R } t_2 \\ & \therefore & \frac{V^2}{ R }(5) & =\frac{\left(\frac{ V }{2}\right)^2}{ R } t_2 \\ & \therefore & 5 & =\frac{t_2}{4}\end{aligned}\)
\(\therefore \quad t_2=20\) મિનિટ

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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