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 = 10 and =5 . The other student takes =1000 and =500 . In the standard arm, both take = 5
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. |
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.
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 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 |
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 R is to be measured using a meter bridge. A student chooses the standard resistance S to be 100 . 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?
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 |
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 |
A metal rod of length 10 cm and a rectangular cross-section of \(1~ \text {cm} \times 1/2~ \text {cm}\) is connected to a battery across opposite faces. The resistance will be:
1. | maximum when the battery is connected across\(1~ \text {cm} \times 1/2~ \text {cm}\) faces. |
2. | maximum when the battery is connected across \(10~ \text {cm} \times 1~ \text {cm}\) faces. |
3. | maximum when the battery is connected across \(10~ \text {cm} \times 1/2~ \text {cm}\) 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)
Consider a simple circuit shown in the figure. R' stands for variable resistance. R' can vary from to infinity. r is the internal resistance of the battery (r<<R<<R).
(a) | Potential drop across AB is nearly constant as R' is varied |
(b) | Current through R' is nearly constant as R' is varied |
(c) | Current I depends sensitively on R |
(d) | \(I \geq { V \over r+R}\) |
Which among the following statements is correct?
1. (a, c)
2. (a, d)
3. (b, d)
4. (c, d)