In the circuit shown in figure find the value of r(internal resistance of the cell) for which power transferred by the cell is maximum

1.  $4\mathrm{\Omega }$

2.  $12\mathrm{\Omega }$

3.  $16\mathrm{\Omega }$

4.  $8\mathrm{\Omega }$

If the voltage across a bulb decreases by 1%, then the percentage change in its power output is :

(1) 1%

(2) 4%

(3) 2%

(4).5%

If a resistance coil is made by joining in parallel two resistances each of 20$\Omega$. An emf of 2V is applied across this coil for 100 seconds. The heat produced in the coil is

(1) 20 J

(2) 10 J

(3) 40 J

(4) 80 J

$$\begin{gathered} \mathrm{Two} \mathrm{battries} \mathrm{of} \mathrm{emf} {\mathrm{\epsilon }}_1, {\mathrm{\epsilon }}_2 \mathrm{and} \mathrm{internal} \mathrm{resistance} {\mathrm{r}}_1, {\mathrm{r}}_2 \mathrm{are} \mathrm{connected} \mathrm{in} \mathrm{parallel} \\ \mathrm{as} \mathrm{shown} \mathrm{in} \mathrm{figure}. \mathrm{The} \mathrm{effective} \mathrm{emf} \mathrm{of} \mathrm{the} \mathrm{circuit} \mathrm{across} \mathrm{A} \mathrm{and} \mathrm{B} \mathrm{is} \end{gathered}$$

1.  $\frac{{\epsilon }_1{\mathrm{r}}_1 + {\epsilon }_2{\mathrm{r}}_2}{{\mathrm{r}}_1 + {\mathrm{r}}_2}$

2.  $\frac{{\epsilon }_1{\mathrm{r}}_2 + {\epsilon }_2{\mathrm{r}}_1}{{\mathrm{r}}_1 + {\mathrm{r}}_2}$

3.  $\frac{{\epsilon }_1{\mathrm{r}}_2 + {\epsilon }_2{\mathrm{r}}_1}{{\mathrm{r}}_1 \times {\mathrm{r}}_2}$

4.  $\frac{{\epsilon }_1{\mathrm{r}}_1 + {\epsilon }_2{\mathrm{r}}_2}{{\mathrm{r}}_1 - {\mathrm{r}}_2}$

Which of the following graphs correctly represents the variation of mobility $\left(\mathrm{\mu }\right)$ of electrons with applied electric field (E) in a metallic conductor?

1.  

2.  

3.  

4.  

The equivalent resistance across AB is :

1.  2R

2.  R/2

3.  4R/3

4.  3R/2

The equivalent resistance between points A and B in the circuit shown in the figure is 

1.  6R

2.  4R

3.  2R

4.  R

The drift velocity of the electrons in a current-carrying  metallic conductor is of the order of 

1.  ${10}^4 \mathrm{m}/\mathrm{s}$

2.  ${10}^8 \mathrm{m}/\mathrm{s}$

3.  ${10}^0\mathrm{m}/\mathrm{s}$

4.  ${10}^{-4}\mathrm{m}/\mathrm{s}$

In the circuit shown in the figure, the effective resistance between A and B is

1.  2$\mathrm{\Omega }$

2.  4$\mathrm{\Omega }$

3.  6$\mathrm{\Omega }$

4.  8$\mathrm{\Omega }$

For the circuit shown in the figure, the value of R must be

1.  3$\mathrm{\Omega }$

2.  4$\mathrm{\Omega }$

3.  5$\mathrm{\Omega }$

4.  6$\mathrm{\Omega }$