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

 1 number of charge carriers can change with temperature T 2 the time interval between two successive collisions can depend on T 3 length of material can be a function of T 4 mass of carriers is a function of T

Which of the above statements is correct?

1. (a, b)

2. (c, d)

3. (b, c)

4. (b, d)

Subtopic:  Derivation of Ohm's Law |
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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 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)

Subtopic:  Wheatstone Bridge |
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In a meter bridge, point D is a neutral point as shown in the figure.

 a. The meter bridge can have no other neutral point for this set of resistances. b. When the jockey contacts a point on the meter wire left of D, current flows to B from the wire. c. When the jockey contacts a point on the meter wire to the right of D, current flows from B to the wire through the galvanometer. d. When R is increased, the neutral point shifts to left.

Which of the above statements is correct?

1. (a, c)

2. (a, d)

3. (b, c)

4. (c, d)

Subtopic:  Meter Bridge & Potentiometer |
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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:

 1 source of emf 2 the electric field produced by charges accumulated on the surface of the wire 3 the charges just behind a given segment of wire which push them just the right way by repulsion 4 the charges ahead

Subtopic:  Current & Current Density |
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Two batteries of emf and internal resistances respectively are connected in parallel as shown in the figure.

1. The equivalent emf ${\mathrm{\epsilon }}_{\mathrm{eq}}$ of the two cells is between

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

Subtopic:  Grouping of Cells |
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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 l= 2.9 cm. He is told to attempt to improve accuracy. Which of the following is a useful way?

 1 He should measure l1 more accurately 2 He should change S to 1000  Ω and repeat the experiment 3 He should change S to 3  Ω and repeat the experiment 4 He should give up hope of more accurate measurement with a meter bridge

Subtopic:  Meter Bridge & Potentiometer |
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Two cells of emf's approximately $$5$$ V and $$10$$ V are to be accurately compared using a potentiometer of length $$400$$ cm.

 1 The battery that runs the potentiometer should have a voltage of $$8$$ V 2 The battery of the potentiometer can have a voltage of $$15$$ V and $$R$$ adjusted so that the potential drop across the wire slightly exceeds $$10$$ V 3 The first portion of $$50$$ cm of the wire itself should have a potential drop of $$10$$ V 4 Potentiometer is usually used for comparing resistances and not voltages
Subtopic:  Meter Bridge & Potentiometer |
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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:

 1 maximum when the battery is connected across 1 cm x 1/2 cm faces. 2 maximum when the battery is connected across 10 cm x 1 cm faces. 3 maximum when the battery is connected across 10 cm x 1/2 cm faces. 4 same irrespective of the three faces.

Subtopic:  Derivation of Ohm's Law |
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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

Subtopic:  Current & Current Density |
57%
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Kirchhoff's junction rule is a reflection of:

 a. conservation of the current density vector b. conservation of charge c. the fact that the momentum with which a charged particle approaches a junction is unchanged (as a vector) as the charged particle leaves the junction d. the fact that there is no accumulation of charges at a junction

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

Subtopic:  Kirchoff's Current Law |
70%
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