A potentiometer wire AB having length L and resistance 12 r is joined to a cell D of emf $$\varepsilon $$ and internal resistance r. A cell C having emf $$\varepsilon $$/2 and internal resistance 3r is connected. The length AJ at which the galvanometer as shown in figure shows no deflection is –

A carbon resistance has a following colour code. What is the value of the resistance ?

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 :