Current Electricity · Question 72

Consider the following two statements. Which of the following is correct?

1. Both (A) and (B) are wrong
2. (A) is correct and (B) is wrong
3. (A) is wrong and (B) is correct
4. Both (A) and (B) are correct

A potentiometer circuit is set up as shown. The potential gradient, across the potentiometer wire, is k volt/cm and the ammeter, present in the circuit, reads 1.0 A when two way key is switched off. The balance points, when the key between the terminals (i) 1 and 2 (ii) 1 and 3, is plugged in, are found to be at length l1 cm and l2 cm respectively. The magnitudes, of the resistors R and X, in ohms, are then, equal, respectively, to [figure]

1. k(l2 - l1) and kl2
2. kl1 and k(l2 - l1)
3. k(l2 - l1) and kl1
4. kl1 and kl2

See the electrical circuit shown in this figure. Which of the following equations is a correct equation for it ? [figure]

1. 2 - i2r2 - 1 - i1r1 = 0
2. - 2 - (i1 + i2)R + i2r2 = 0
3. 1 - (i1 + i2)R + i1r1 = 0
4. 1 - (i1 + i2)R - i1r1 = 0

A wire of resistance 12 ohms per metre is bent to form a complete circle of radius 10 cm. The resistance between its two diametrically opposite points, A and B as shown in the figure is [figure]

1. 3
2. 6
3. 6
4. 0.6

A student measures the terminal potential difference (V) of a cell (of emf and internal resistance r) as a function of the current (I) flowing through it. The slope, and intercept, of the graph between V and I, then respectively, equal

1. -r and
2. r and -
3. - and r
4. and -r

The mean free path of electrons in a metal is 4 10-8 m. The electric field which can give on an average 2 eV energy to an electron in the metal will be in units V/m

1. 5 10-11
2. 8 10-11
3. 5 107
4. 8 107

[figure] In the circuit shown, the current through the 4 resistor is 1 amp when the points P and M are connected to a d.c. voltage source. The potential difference between the points M and N is

1. 0.5 volt
2. 3.2 volt
3. 1.5 volt
4. 1.0 volt

A wire of a certain material is stretched slowly by ten percent. Its new resistance and specific resistance become respectively

1. both remain the same
2. 1.1 times, 1.1 times
3. 1.2 times, 1.1 times
4. 1.21 times, same

A cell can be balanced against 110 cm and 100 cm of potentiometer wire, respectively without and with being short circuited through a resistance of 10 . Its internal resistance is

1. 2.0 ohm
2. zero
3. 1.0 ohm
4. 0.5 ohm

An electric kettle takes 4 A current at 220 V. How much time will it take to boil 1 kg of water from temperature 20 ? The temperature of boiling water is 100

1. 12.6 min
2. 4.2 min
3. 6.3 min
4. 8.4 min