MCQ
41. Suppose, double the voltage in a simple de circuit and cut the resistance in half, then the current will-
Become four times as great
Become twice as great
Stay the same as it was before
Become half as great
42. The internal resistance of a cell of e.m.f 2V is 0.1Ω It is connected to a resistance of 3.9Ω. The voltage across the cell is-
0.5V
1.9V
1.95V
2V
43. What will be the internal resistance of cell, if it supplies 0.9A current through 2Ω resistor and 0.3A current through 7Ωresistor?
0.9Ω
1.2Ω
0.5Ω
1Ω
44. The true statement for a series and a parallel de circuit is--
ব্যাখ্যা: Powers are additive in both series and Parrallel. Currents are additive in parallel circuits whereas voltages are additive in series circuit.
powers are additive
current are additive
element have individual current
voltage are additive
45. A 50V battery is connected across 10Ω resistor. The current is 4.5 A. The internal resistance of the battery is-
zero
0.5Ω
5Ω
1.1Ω
46. What will be the current in 2 seconds from a wire of having 10 mC charge flow and 2.5mm cross sectional area?
25mA
5mA
20mA
4mA
47. Kirchhoff's current law at a junction deals with-
ব্যাখ্যা: Kirchhoff's Current Law (KCL) is Kirchhoff's first law deals with the conservation of charge entering and leaving a junciton
Conversation of energy
Conversation of momentum
Conversation of charge
Conversation of angular momentum
48. Kirchhoff's voltage law deals with—
Conversation of energy
Conversation of momentum
Conversation of charge
Conversation of angular momentum
49. Two equal resistances are connected in series across a certain supply. If the resistances are now connected in parallel, the power produced will become-
ব্যাখ্যাঃ if two equal resistance connected in series across a certain supply are now connected in parallel across the same supply, the power produced will be four times that of series connection.
two-times
four times
one-half
one-fourth
50. Permeability in a magnetic circuit corresponds to--in electric circuit.
conductivity
conductance
resistivity
resistance
51. A 40W bulb is connected in parallel with room heater. What will happen if we turn off bulb?
ব্যাখ্যা: In parallel connection, the voltage across the element is constant. Therefore, the voltage across heater remains same.
Heater output will increase
Heater output will decrease
Heater output will remains same
None of the above
52. The total resistance of circuit by connecting 50 resistance of 1/4 Ω in parallel is---
50/4Ω
200Ω
4/50Ω
1/200Ω
53. Two resistors of 18Ω and 5Ω are connected in series to a 230 volt supply. The current is-
12A
10A
10.5A
9.5A
54. An external resistance R is connected to a cell of internal resistance r. The maximum current flows in the external resistance when-
R<r
R=r
R>r
None of the above
55. A wire has a resistance of 122. It is bent in the form of a circle. The effective resistance between the two points on any diameter of the circle is--
6Ω
12Ω
3Ω
24Ω
56. Three resistance 14.5Ω, 25.5Ω and 60Ω are connected in series across 200V. What will be the voltage drop across 14.5Ω?
29V
14V
13.5V
18V
57. What happens if an electric bulb rated at 220V is connected to 220V, 5 Hz ac source? The bulb-
ব্যাখ্যাঃ When you give 5Hz supply, frequency is too low. Normally when 50 Hz (50 times a second AC is given, it will get max volts twice in each cycle, that is it gets varing voltage from 0 to 220'a hundred times a second, in negative and positive cycles), the white hot blulb filament has no time to cool. Hence it appears to us as glowing continuously. But when you drastically reduce to 5 Hz it has times to cool off and again get white when hot. You will observe the blub will flash at rate of 10 times per seconde
does not glow
fuses
glows continuously
glows intermittently
58. Electrical appliances are connected in parallel because it-
Is a simple circuit
Draws less current
Results in reduced power loss
Makes the operation of appliances independent of each other
59. The resistance of each arm of Wheatstone bridge is 10 Ω. A resistance of 10Ω is connected in series with the galvanometer. The equivalent resistance across the battery will be-
40 Ω
20 Ω
30 Ω
10 Ω
60. If a galvanometer is open circuited in a balanced Wheatstone bridge, the current in various resistors of Wheatstone bridge will---
Increase
Decrease
Not change
Cannot say anything