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Electricity — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10ScienceElectricity1 Mark
MCQ
For two statements are given $-$ one labelled Assertion $(A)$ and the other labelled Reason $(R). $ Select the correct answer to these questions from the codes $\ce{(a), (b), (c)}$ and $(d)$ as given below :
Assertion : The coil of a heater is cut into two equal halves and only one of them is used into heater. The heater will now require half the time to produce the same amount of heat.
Reason : The heat produced is directly proportional to square of current.
  • A
    Both $A$ and $R$ are true, and $R$ is correct explanation of the assertion.
  • ✓
    Both $A$ and $R$ are true, but $R$ is not the correct explanation of the assertion.
  • C
    $A$ is true, but $R$ is false.
  • D
    $A$ is false, but $R$ is true.
✓

Answer

Correct option: B.
Both $A$ and $R$ are true, but $R$ is not the correct explanation of the assertion.
Since in the given case, the voltage is same,
Therefore, $\text{H}=\frac{\text{V}^2}{\text{R}}\text{t}=\text{constant.}$
Hence, if $R$ is halved, $t$ must be halved.

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