Question 379: Current Electricity

Question

In the given circuit the the internal resistance of the 18 V cell is negligible. If R
1
= 400 $\Omega $, R
3
= 100 $\Omega $ and R
4
= 500 $\Omega $ and the reading of an ideal voltmeter across R
4
is 5V, then the value of R
2
will be :

Accepted Answer

Voltage accross resistance R
4
= 5 V
$ 	herefore $   IR
4
= 5 V
$ \Rightarrow $   500 $ 	imes $ I = 5
$ \Rightarrow $   I = ${1 \over {100}}$ A
$ 	herefore $   Voltage across resistor R
3
= ${1 \over {100}}\left( {100} ight)$ = 1 A
$ 	herefore $   Total drop in resistance R
3
and R
4
= 5 + 1 = 6V
So, voltage accross R
2
resistance is also 6V as R
3
, R
4
and R
2
are in parallel
$ 	herefore $   Voltage accross R
1
resistor R
1
resistor = 18 $-$ 6 = 12 V
$ 	herefore $   Current through R
1
resistor = ${{12} \over {400}}$ = ${3 \over {100}}$ A
$ 	herefore $   Current through R
2
resistor
= ${3 \over {100}} - {1 \over {100}}$
=  ${2 \over {100}}$ A
$ 	herefore $   $\left( {{2 \over {100}}} ight)$  R
2
= 6
$ \Rightarrow $   R
2
= 300 $\Omega $

Answer

300 $\Omega $

Answer

450 $\Omega $

Answer

550 $\Omega $

Answer

230 $\Omega $

Current Electricity

In the given circuit the the internal resistance of the 18 V cell is negligible. If R 1 = 400 \Omega , R 3 = 100 \Omega and R 4 = 500 \Omega and the reading of an ideal voltmeter across R 4 is 5V, then the value of R 2 will be :

Choose the correct answer: