Temperature dependence of resistivity of semiconductors, insulators, and metals is significantly based on the following factors:
(a) | number of charge carriers can change with temperature . |
(b) | the time interval between two successive collisions can depend on . |
(c) | length of material can be a function of . |
(d) | mass of carriers is a function of . |
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 is to be carried out using a Wheatstone bridge. Two students perform an experiment in two ways. The first students take and The other student takes and In the standard arm, both take 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 and can be measured. |
(c) | If the student uses large values of and 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. |
Choose the correct option from the given ones:
1. (a) and (c) only
2. (c) and (d) only
3. (b) and (c) only
4. (c) and (d) only
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)
Consider a current carrying wire (current ) in the shape of a circle. Note that as the current progresses along the wire, the direction of (current density) changes in an exact manner, while the current 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. |
Two batteries of emf and internal resistances respectively are connected in parallel as shown in the figure.
1. | The equivalent emf of the two cells is between |
2. | The equivalent emf is smaller than |
3. | The is given by always |
4. | is independent of internal resistances |
A resistance is to be measured using a meter bridge. A student chooses the standard resistance to be He finds the null point at He is told to attempt to improve accuracy. Which of the following is a useful way?
1. | He should measure more accurately |
2. | He should change to and repeat the experiment |
3. | He should change to and repeat the experiment |
4. | He should give up hope of more accurate measurement with a meter bridge |
Two cells of emf's approximately V and V are to be accurately compared using a potentiometer of length cm.
1. | The battery that runs the potentiometer should have a voltage of V |
2. | The battery of the potentiometer can have a voltage of V and adjusted so that the potential drop across the wire slightly exceeds V |
3. | The first portion of cm of the wire itself should have a potential drop of V |
4. | Potentiometer is usually used for comparing resistances and not voltages |
A metal rod of length 10 cm and a rectangular cross-section of is connected to a battery across opposite faces. The resistance will be:
1. | maximum when the battery is connected across faces. |
2. | maximum when the battery is connected across faces. |
3. | maximum when the battery is connected across faces. |
4. | same irrespective of the three faces. |
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. |
(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) |