Current Electricity · Question 68

If voltage across a bulb rated 220 volt-100 watt drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is

1. 20%
2. 2.5%
3. 5%
4. 10%

In the circuit shown in the figure, if the potential at point A is taken to be zero, the potential at point B is [figure]

1. +1 V
2. -1 V
3. +2 V
4. -2 V

A current of 2 A flows through a 2 Ω resistor when connected across a battery. The same battery supplies a current of 0.5 A when connected across a 9 Ω resistor. The internal resistance of the battery is

1. 0.5 Ω
2. 1/3 Ω
3. 1/4 Ω
4. 1 Ω

If power dissipated in the 9 Ω resistor in the circuit shown is 36 watt, the potential difference across the 2 Ω resistor is [figure]

1. 4 volt
2. 8 volt
3. 10 volt
4. 2 volt

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