Question 290: Current Electricity

Question

An ideal battery of 4 V and resistance R are connected in series in the primary circuit of a potentiometer of length 1 m and  esistance 5 $$\Omega $$. The value of R, to give a potential difference of 5 mV across 10 cm of potentiometer wire, is :

Accepted Answer

Let current flowing in the wire is i.
$$ 	herefore $$  i = $$\left( {{4 \over {R + 5}}} ight)A$$
If resistance of 10 m length of wire is x
then x = 0.5 $$\Omega $$ = 5 $$ 	imes $$ $${{0.1} \over 1}$$ $$\Omega $$
$$ 	herefore $$   $$\Delta $$V = P.d. on wire = i. x
5 $$ 	imes $$ 10
$$-$$3
= $$\left( {{4 \over {R + 5}}} ight)$$.(0.5)
$$ 	herefore $$   $${{4 \over {R + 5}}}$$ = 10
$$-$$2
or   R + 5 = 400 $$\Omega $$
$$ 	herefore $$   R = 395 $$\Omega $$

Answer

480 $$\Omega $$

Answer

495 $$\Omega $$

Answer

490 $$\Omega $$

Answer

395 $$\Omega $$

Current Electricity

An ideal battery of 4 V and resistance R are connected in series in the primary circuit of a potentiometer of length 1 m and esistance 5 $\Omega $. The value of R, to give a potential difference of 5 mV across 10 cm of potentiometer wire, is :

Choose the correct answer: