# Homework Help: Ammeter and Voltmeter question?

1. Oct 25, 2011

### vkash

1. The problem statement, all variables and given/known data

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

2. Relevant equations

You know that so i needn't to provide

3. 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 [tex]\frac{V}{Rv+Ra}[\tex] In second case a new resistance is introduced in the circuit so net resistance is Rv+Ra+R. Current in this case is $\frac{V}{Rv+Ra+R}[\itex]. A we can see quit clearly that [itex]\frac{V}{Rv+Ra[/sub}[\itex] > [itex]\frac{V}{Rv+Ra+R}$
so current in second case (say I2) is greater than current in first case(say I1)
Potential difference between the voltmeter in first case is [itex]RvI1[\itex] and in second case is [itex]RvI2[\itex]. I2<i1 so potential difference between the voltmeter in first case should greater than that in second case.
so what's the conclusion; that is ammeter reading as well as voltmeter reading will drop so. Option B is correct for me.
As always i ask. where am i wrong?
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.

Last edited: Oct 25, 2011
2. Oct 25, 2011

### ehild

It is wrong.

Read the problem again, especially the text in blue. Draw the circuit diagram, and find out how the resistances are connected.

ehild

Last edited: Oct 25, 2011
3. Oct 25, 2011

### vkash

thanks buddy. Question solved.