### MCQs of Current Electricity

Showing 41 to 50 out of 119 Questions
41.
The tungsten filament of bulb has resistance equal to 18Ω at 20ºC temperature. 0.185 A of current flows, when 30 V is connected to it. If α = 4.5 x 10-3 K-1 for a tungsten, then the temperature of the filament is _____ .
 (a) 2070.7 K (b) 2050.5 K (c) 2000 K (d) zero
42.
6 batteries, each of 2.0 volts are connected in series so that they are helping each other. Internal resistance of each is 0.5 Ω. They are being charged using a direct voltage supply of 110 volts. To control the current, a resistance of 46 Ω, is used in the series.So power drawn from the supply is _____ and power dissipated as heat is _____
 (a) 110, 296 (b) 220, 196 (c) 110, 24 (d) 220, 24
43.
An electric current of 5A is divided in three branches forming a parallel combination. The lengths of the wires in the three branches are in the proportion 2 : 3 : 4 and their radii are in the proportion 3 : 4 : 5. The currents in each branch if the wires are of the same material are _____ , _____ and _____ respectively.
 (a) 0, 1 A, 2 A (b) 1 A, 2.82 A, 3.92 A (c) 60 A, 70 A, 50 A (d) 1.40 A, 1.66 A, 1.94 A
44.
200 Ω resistor is connected in one of the gaps of the meterbridge. Series combination of X Ω and 50 Ω resistors is connected in the second gap. Here unknown resistance X Ω is kept in a heat bath at a certain temperature. The unknown resistance and its temperature is _____ and _____ respectively if the balance point is obtained at 50 cm. The total length of the wire of the meterbridge is equal to 1 meter. The resistance of the unknown resistance at 0 ºC temperature is equal to 100 Ω, α = 0.5 x 10-3 ºC-1 for the material of the X Ω resistors.
 (a) 100 Ω, 100ºC (b) 150 Ω, 100ºC (c) 100 Ω, 50ºC (d) 100 Ω, 150ºC
45.
A stream of electrons moves from the electron gun to a screen of a television. The electric current of the 10 μ A is constituted. Calculate the number of electrons striking the screen at every second. Also calculate the magnitude of the charges striking the screen in one minute.
 (a) n = 6.25 x 1013 electron/s. Q : -600 μC (b) n = 1.50 x 1013 electron/s. Q : -500 μC (c) n = 3.25 x 1013 electron/s. Q : -160 μC (d) n = 4.50 x 1013 electron/s. Q : -400 μC
46.
An n-type semiconductors has 4 x 10-3 meter width, 25 x 10-5 meter thickness and 6 x 10-2 meter length. 4.8 mA current is flowing through it. Here voltage is applied parallel to the length of the semiconductor. Calculate the current density. The density of the free electron is equal to 1022 m-3. What will be the time taken by the electron across the length of the semiconductor ?
 (a) 4.8 x 103 Am-2, 2 x 10-2 s (b) 3.4 x 103 Am-2, 8 x 10-2 s (c) 2.8 x 103 Am-2, 8 x 10-2 s (d) 6.2 x 103 Am-2, 8 x 10-2 s
47.
The resistance of one aluminium and one copper wires, having identical lengths is equal. Which of the two wires will be lighter ? ρAl = 2.63 x 10-8 Ω m, ρCu = 1.72 x 10-8 Ω m the density of the aluminium is 2.7 x 103 kg m-3 and density of copper is 8.9 x 103 kg m-3.
 (a) Aluminium (b) Copper (c) Both (A) and (B) (d) None of these
48.
The length of the potentiometer wire is 200 cm. For a given cell, the null point is obtained at 80 cm. What will be the length of the wire required for balancing the cell if the length of the same wire is made 300 cm ?
 (a) 200 cm (b) 120 cm (c) 150 cm (d) 180 cm
49.
A battery having an emf of 12 volt and an internal resistance of 2 Ω is connected to another battery having an emf of 18 volt and an internal resistance of 2 Ω in such a way that they are opposing each other and the circuit is closed. Calculate the following :

(1) current flowing in the circuit.

(2) electrical power in the two batteries.

(3) terminal voltage of the two batteries.

(4) electric power consumed in the batteries.

 (a) (1) 1.5 A (2) 18 W, 27 W (3) 15 V, 15 V (4) 4.5 W, 4.5 W (b) (1) 2.5 A (2) 20 W, 27 W (3) 16 V, 16 V (4) 5.2 W, 5.2 W (c) (1) 0 A (2) 17 W, 15 W (3) 12 V, 12 V (4) 3.5 W, 3.5 W (d) (1) 1 A (2) 16 W, 24 W (3) 18 V, 18 V (4) 4.5 W, 4.5 W
50.
An electric kettle has two heating coils. When one of the coils is switched on, a given quantity of water in the kettle starts boiling in 6 minutes. When the other coil only is switched on, then the same amount of water starts boiling in 8 minutes. If the two coils are switched on in parallel, how much time will the same amount of water take to boil ? Each time the voltage applied is the same.
 (a) 3.43 min (b) 1.28 min (c) 4.36 min (d) 2.25 min
Showing 41 to 50 out of 119 Questions