71.

Three identical bulbs connected in series across an accumulator consumes 20 W power. If the bulbs are connected in parallel to the same source, the power consumed is

• 20 W

• 60 W

• 180 W

• 120 W

The resistances in the four arms of a Wheatstone network in cyclic order are 5 Ω, 2 Ω, 6 Ω and 15 Ω. 1f a current of 2.8 A enters the junction of 5 Ω and 15 Ω, then the current through 2 Ω resistor is

• 1.5 A

• 2.8 A

• 2.1 A

• 1.4 A

Pick out the wrong feature about carbon resistors

• Compact

• Inexpensive

• Relatively sensitive to temperature

• Mostly used for higher resistor values

The number of electrons per second flowing through any cross-section of the wire carrying current of 1 A is

• 3.12 × 10¹⁶ 

• 1.6 × 10¹⁸

• 6.25 × 10¹⁸

• 3.12 × 10¹⁸

Identify the mismatch of the following

• Photo diode — optical signal

• LED — spontaneous emission

• Diode laser — stimulated emission

• Solar cell — electrical energy into light

The resistance of a 10 m long wire is 10 Ω. Its length is increased by 25% by stretching the wire uniformly. Then the resistance of the wire will be

• 12.5 Ω

• 14.5 Ω

• 15.6 Ω

• 16.6 Ω

If 2 A of current is passed through CuSO₄ solution for 32 s, then the number of copper ions deposited at the cathode will be

• 4 × 10²⁰

• 2 × 10²⁰

• 4 × 10¹⁹

• 2 × 10¹⁹

In a potentiometer experiment, when three cells A, B and C are connected in series the balancing length is found to be 740 cm. If A and B are connected in series balancing length is 440 cm and for B and C connected in series that is 540 cm. Then the emf of E_A, E_B and E_c are espectively (in volts)

• 1, 1.2 and 1.5

• 1, 2 and 3

• 1.5, 2 and 3

• 1.5, 2.5 and 3.5

Find the true statement.

• Ohm's law is applicable to all conductors of electricity

• In an electrolyte solution, the electric current is mainly due to the movement of electrons.

• The resistance of carbon decreases with the increase of temperature.

• Specific resistance of a wire depends upon its dimension.

The tolerance level of a resistor with the colour code red, blue, orange, gold is

• ± 5 %

• ± 10 %

• ± 20 %

• ± 40 %