The power dissipated in the circuit shown in

the figure is 30 Watt. The value of R is :

1. $20\mathrm{\Omega }$

2. $15\mathrm{\Omega }$

3. $10\mathrm{\Omega }$

4. $30\mathrm{\Omega }$

 Consider the following two statements :

1. Kirchhoff's junction law follows from the conservation of charge.

2. Kirchhoff's loop law follows from the conservation of energy.

     Which of the following is correct?

(a) Both (A) and (B) are wrong

(b) (A) is correct and (B) is wrong

3. (A)  is wrong and (B) is correct

4. Both (A) and (B) are correct

If power dissipated in the 9$\mathrm{\Omega }$ resistor in the circuit shown is 36 W, the potential difference across the 2$\mathrm{\Omega }$ resistor is

1. 8 V
2. 10 V
3. 2 V
4. 4 V

A current of 2A flows through a 2$\mathrm{\Omega }$ resistor

when connected across a battery. The same

battery supplies a current of 0.5 A when

connected across a 9$\mathrm{\Omega }$ resistor. The internal

resistance of the battery is 

1. $1/3\mathrm{\Omega }$                   

2. $1/4\mathrm{\Omega }$

3. $1\mathrm{\Omega }$                       

4. $0.5\mathrm{\Omega }$

A potentiometer circuit is set up as shown.The potential gradient across the potentiometer wire, is k volt/cm and the ammeter, present in the circuit, reads 1.0A when two way key is switched off. The balance points, when the key between the terminals (i) 1 and 2 (ii) 1and 3, is plugged in, are found to be at lengths $l_{1}cm<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>l_{2}cm$ respectively.The magnitudes, of the resistors R and X, in ohm, are then, equal, respectively, to

(a)$k\left(l_2-l_1\right)<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>k{l}_2$

(b)$k{l}_1<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>k\left(l_2-l_1\right)$

(c)$k\left(l_2-l_1\right)and<mspace\; width="1em"></mspace>k{l}_1$

(d)$k{l}_1<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>k{l}_2$

Which one of the following bonds produces a solid that reflects light in the visible region and whose electrical conductivity decreases with temperature and has high melting point?

(1) metallic bonding

(2) van der Waals'bonding

(3) ionic bonding 

(4) covalent bonding

In the circuit in the figure, if the potential at point A is taken to be zero, the potential at point B is :

1. -1V                                          2. +2V

3. -2V                                          4. +1V

A cell having an emf $\mathrm{\epsilon }$ internal resistance r is connected across a variable external  resistance R. As the resistance R is increased, the plot of potential difference V across R is given by

1.    

2. 

3. 

4. 

A ring is made of a wire having a resistance 

${\mathrm{R}}_0=12\mathrm{\Omega }$. Find the points A and B, as shown

in the figure, at which a current carrying 

conductor should be connected so that the 

resistance R of the sub circuit between these

points is equal to 8/3$\mathrm{\Omega }$

1. $\frac{{\mathrm{l}}_1}{{\mathrm{l}}_2}=\frac{5}{8}$                   
2. $\frac{{\mathrm{l}}_1}{{\mathrm{l}}_2}=\frac{1}{3}$
3. $\frac{{\mathrm{l}}_1}{{\mathrm{l}}_2}=\frac{3}{8}$                   
4. $\frac{{\mathrm{l}}_1}{{\mathrm{l}}_2}=\frac{1}{2}$