Temperature dependence of resistivity $\mathrm{\rho }$(T) of semiconductors, insulators, and metals is significantly based on the following factors:
 

Which of the above statements is correct?

1. (a, b)

2. (c, d)

3. (b, c)

4. (b, d)

The measurement of an unknown resistance R is to be carried out using a Wheatstone bridge. Two students perform an experiment in two ways. The first students take ${\mathrm{R}}_2$ = 10 $\mathrm{\Omega }$ and ${\mathrm{R}}_1$ =5 $\mathrm{\Omega }$. The other student takes ${\mathrm{R}}_2$ =1000 $\mathrm{\Omega }$ and ${\mathrm{R}}_1$ =500 $\mathrm{\Omega }$. In the standard arm, both take ${\mathrm{R}}_3$ = 5 $\mathrm{\Omega .}$

Both find $\mathrm{R}=\frac{{\mathrm{R}}_2}{{\mathrm{R}}_1}{\mathrm{R}}_3=\mathrm{10 }\mathrm{\Omega }$ within errors.

(a) The errors of measurement of the two students are the same.

(b) Errors of measurement do depend on the accuracy with which ${\mathrm{R}}_2$ and ${\mathrm{R}}_1$ can be measured.

(c) If the student uses large values of ${\mathrm{R}}_2$ and ${\mathrm{R}}_1$, the currents through the arms will be feeble. This will make the determination of the null point accurately more difficult.

(d) Wheatstone bridge is a very accurate instrument and has no errors of
measurement.

1. (a, c)

2. (c, d)

3. (b, c)

4. (c, d)

In a meter bridge, point D is a neutral point as shown in the figure.
 

                                    

Which of the above statements is correct?

1. (a, c)

2. (a, d)

3. (b, c)

4. (c, d)

Consider a current carrying wire (current I) in the shape of a circle. Note that as the current progresses along the wire, the direction of j (current density) changes in an exact manner, while the current I remains unaffected. The agent that is essentially responsible for it is:

Two batteries of emf ${\epsilon }_1\text{ and }{\epsilon }_2 ({\epsilon }_2>{\epsilon }_1)$ and internal resistances ${\mathrm{r}}_1 \mathrm{and} {\mathrm{r}}_2$ respectively are connected in parallel as shown in the figure.

1. The equivalent emf ${\mathrm{\epsilon }}_{\mathrm{eq}}$ of the two cells is between ${\epsilon }_1\text{ and }{\epsilon }_2.\text{ i.e, }{\epsilon }_1<{\epsilon }_{eq}<{\epsilon }_2$

2. The equivalent emf ${\mathrm{\epsilon }}_{\mathrm{eq}}$ is smaller than ${\mathrm{\epsilon }}_1$

3. The ${\mathrm{\epsilon }}_{\mathrm{eq}}$ is given by ${\epsilon }_{eq}={\epsilon }_1+{\epsilon }_2$ always

4. ${\mathrm{\epsilon }}_{\mathrm{eq}}$ is independent of internal resistances ${\mathrm{r}}_1 \mathrm{and} {\mathrm{r}}_2$

A resistance R is to be measured using a meter bridge. A student chooses the standard resistance S to be 100 $\mathrm{\Omega }$. He finds the null point at l₁ = 2.9 cm. He is told to attempt to improve accuracy. Which of the following is a useful way?
 

Two cells of emf's approximately 5 V and 10 V are to be accurately compared using a potentiometer of length 400 cm.
 

A metal rod of length 10 cm and a rectangular cross-section of 1 cm x 1/2 cm is connected to a battery across opposite faces. The resistance will be:

 

Which of the following characteristics of electrons determines the current in a conductor?

1. Drift velocity alone

2. Thermal velocity alone

3. Both drift velocity and thermal velocity

4. Neither drift nor thermal velocity

Kirchhoff's junction rule is a reflection of:

Which of the above statements are correct?
1. b and c
2. a and c
3. b and d
4. c and d