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. $\frac{L{E}_{0}r}{(r+r_1)1}$

A filament bulb (500 W, 100 V) is to be used in a 230 V main supply. When a resistance R is connected in series, it works perfectly and the bulb consumes 500 W. The value of R is :

1.  230 $\mathrm{\Omega }$

2.  46 $\mathrm{\Omega }$

3.  26 $\mathrm{\Omega }$

4.  13 $\mathrm{\Omega }$

A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 m long. When the resistance, R, connected across the given cell, has values of (i) infinity (ii) 9.5, the 'balancing lengths, on the potentiometer wire, are found to be 3m and 2.85 m, respectively. 
The value of internal resistance of the cell is (in ohm) :

1. 0.25

2. 0.95

3. 0.5

4. 0.75