- #1
vkash
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Homework Statement
A ammeter and a voltmeter are joined in series to a cell . Their reading are A and V respectively. If a resistance is now joined in parallel with voltmeter,
(a) Both A and V will increase
(b) Both A and V will decrease
(c) A will decrease V will increase
(d) A will increase V will decrease
Homework Equations
You know that so i needn't to provide
The Attempt at a Solution
For me option 'B' is correct
why?
because; in first case net resistance in Rv+Ra so current in the circuit is \frac{V}{R<sub>v</sub>+R<sub>a</sub>}[\tex] In second case a new resistance is introduced in the circuit so net resistance is R<sub>v</sub>+R<sub>a</sub>+<b>R</b>. Current in this case is \frac{V}{R<sub>v</sub>+R<sub>a</sub>+<b>R</b>}[\itex]. A we can see quit clearly that \frac{V}{R&lt;sub&gt;v&lt;/sub&gt;+R&lt;sub&gt;a[/sub}[\itex] &amp;gt; \frac{V}{R&amp;lt;sub&amp;gt;v&amp;lt;/sub&amp;gt;+R&amp;lt;sub&amp;gt;a&amp;lt;/sub&amp;gt;+&amp;lt;b&amp;gt;R&amp;lt;/b&amp;gt;}&lt;br /&gt; so current in second case (say I&lt;sub&gt;2&lt;/sub&gt;) is greater than current in first case(say I&lt;sub&gt;1&lt;/sub&gt;) &lt;br /&gt; Potential difference between the voltmeter in first case is R&amp;lt;sub&amp;gt;v&amp;lt;/sub&amp;gt;I&amp;lt;sub&amp;gt;1&amp;lt;/sub&amp;gt;[\itex] and in second case is R&amp;amp;lt;sub&amp;amp;gt;v&amp;amp;lt;/sub&amp;amp;gt;I&amp;amp;lt;sub&amp;amp;gt;2&amp;amp;lt;/sub&amp;amp;gt;[\itex]. I&amp;amp;lt;sub&amp;amp;gt;2&amp;amp;lt;/sub&amp;amp;gt;&amp;amp;amp;lt;i&amp;amp;lt;sub&amp;amp;gt;1&amp;amp;lt;/sub&amp;amp;gt; so potential difference between the voltmeter in first case should greater than that in second case.&amp;amp;lt;br /&amp;amp;gt; so what&amp;amp;amp;#039;s the conclusion; that is ammeter reading as well as voltmeter reading will drop so. Option B is correct for me.&amp;amp;lt;br /&amp;amp;gt; As always i ask. &amp;amp;lt;b&amp;amp;gt; where am i wrong?&amp;amp;lt;/b&amp;amp;gt;&amp;amp;lt;br /&amp;amp;gt; &amp;amp;lt;b&amp;amp;gt;sorry friends i tried to change / \ and some others, but none work with tex itex so try understand as it is written or just put answer.&amp;amp;lt;/b&amp;amp;gt;&lt;/sub&gt;
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thanks buddy
