In the given circuit the the internal resistance of the 18 V cell is negligible. If R₁ = 400 $$\Omega $$, R₃ = 100 $$\Omega $$ and R₄ = 500 $$\Omega $$ and the reading of an ideal voltmeter across R₄ is 5V, then the value of R₂ will be :

When the switch S, in the circuit shown, is closed, then the value of current i will be :

A resistance is shown in the figure. Its value and tolerance are given respectively by :

Drift speed of electrons, when 1.5 A of current flows in a copper wire of cross section 5 mm², is $$\upsilon $$. If the electron density in copper is 9 $$ \times $$ 10²⁸/m³ the value of $$\upsilon $$. in mm/s is close to (Take charge of electron to be = 1.6 $$ \times $$ 10^$$-$$19C)