Three resistances P, Q, R each of 2Ω and an unknown resistance S form the four arms of a Wheatstone’s bridge circuit. When the resistance of 6 Ω is connected in parallel to S the bridge gets balanced. What is the value of S?

1. 2 $\Omega$

2. 3 $\Omega$

3. 6 $\Omega$

4. 1 $\Omega$ 

Six similar bulbs are connected as shown in the figure with a DC source of emf E and zero internal resistance.

The ratio of power consumption by the bulbs when (i) all are glowing and (ii) in the situation when two from section A and one from section B are glowing, will be:

1. 2: 1

2. 4: 9

3. 9: 4

4. 1: 2

In a discharge tube ionization of enclosed gas is produced due to collisions between:

1. positive ions and neutral atoms/molecules

2. negative electrons and neutral atoms/molecules

3. photons and neutral atoms/molecules

4. neutral gas atoms/molecules

In the circuit shown cells, \(A\) and \(B\) have negligible resistance. For \(V_A =12 ~\text{V}\), \(R_1 = 500 ~\Omega \), and $\mathrm{}$\(R = 100 ~\Omega \) the galvanometer \((\text{G}) \) shows no deflection. The value of \(V_B\) is: 
     

1. \(4\) V
2. \(2\) V
3. \(12\) V
4. \(6\) V

A potentiometer wire of length L and a resistance r are connected in series with a battery of e.m.f. $E_0$and resistance $r_1$. An unknown e.m.f. is balanced at a length l of the potentiometer wire. The e.m.f. E will be given by :

1. $\frac{LE{ }_{0}r}{l{r}_1}$

2. $\frac{E_{0}r}{(r+r_1)}·\frac{l}{L}$

3. $\frac{E_{0}l}{L}$

4. $\frac{L{E}_{0}r}{(r+r_1)1}$