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: