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### Electric and Magnetism

66.n-equal capacitors are first connected in series and then in parallel. The the ratio of maximum to minimum capacitance [2075]

n2

1/n2

n

1/n

67.A wire of resistance 12Ω is bent to form a circle.The effective resistance between the two points on any diameter of circle is [2075]

12Ω

9Ω

6Ω

3Ω

68. The resistance of an ideal ammeter is [2075]

0

low

high

infinite

69. A 10 eV electron is circulating in a plane at right angles to a uniform field of magnetic induction 10-4, the orbital radius of the electron is [2075]

18cm

16cm

11cm

9cm

70. Whenever the magnetic flux linked with a coil changes,there is emf induced in the circuit the emf last [2075]

For a short time

For a long time

Forever

so long as the change in flux takes place

69. Wheat stone bridge is used to measure [2074]

emf

potential

current

resistance

70. Magnetism of a magnet [2074]

is zero at absolute zero temperature

increase with temperature

is maximum at curie temperature

becomes practically zero above curie temperature

71. The self inductance of coil is MH. If a current of 2a is flown. What is the magnetic flux through coil? [2074]

0.02 Wb

0.01 Wb

0.05 Wb

10 Wb

64. An isolated conducting sphere is given a positive charge. It's mass [2073]

increases

decreases

remains constant

may increase or decrease depending on the material

65. Three capacitors each of capacitance 3pF are connected in series. The net capacitance is [2073]

1μF

(1/3)μF

3μF

9μF

66. Kirchoff's voltage law is based on the principle of conservation of. [2073]

charge

energy

momentum

mass of charges

67. A charged particle is in a strong magnetic field. Then its kinetic energy [2073]

increase

decrease

remain constant

increase and become constant

68. The self-inductance of a straight wire is [2073]

zero

infinity

negative

positive

71. On increasing the reserve bias to a large value in a p-n junction diode, the current [2073]

increase slowly

remains fixed

decreases slowly

suddenly increases

67. A 25W, 120V lamp and 100W, 120V lamp are connected in series across a 120V line. Which lamp will burn more brightly[2072]

25W, 120V

100W, 120V

Both will have same brightness

Alternatively both may be bright, one at a time.

70. A 0 - 100mA resistance 1ft is to be converted to an ammeter in the range of 0-1A. We have to use shunt [2072]

0.1Ω

0.111Ω

0.055Ω

68. A system of three charges may be in equilibrium . If they are placed[2071]

On a straight line

On corners of equilateral triangle

On three corners of rectangle

On the corners of a cube

69. The radius of Earth 6400 km. The capacitance is [2071]

6400 MF

6400 F

1 F

711 μF

70. Two wire of same material have lengths L and 2L and are cross reaction areas 4A and A respectively. The ratio of their specific resistance would be [2071]

1:1

1:8

8:1

1:2

71. The magnetic field induction inside a long solenoid is[2071]

zero

0ni

μ0ni

μni

64. Three capacitor of capacitance 3µF, 9µF and 18µF are connected first in series and then I parallel. the ratio of C equivalent capacitance in two cases (CI/CP) will be[2070]/p>

1:15

15:1

1:1

1:3

65. Three equal registers each of resistance 'r' are connected to form a triangle. The equivalent resistance across any two comes of the triangle is.....[2070]

2r

r/3

2r/3

3r

66. The resistance of two lamp are in ratio of 1:2. Their wattage will be in the ratio of [2070]

1:2

2:1

4:1

1:4

67. The energy stored in 50mH inductor carrying a current of 4A is ....... [2070]

0.1 J

0.4 J

0.3 J

0.01 J

68. The alternating current in an LCR circuit is maximum when [2070]

XL = 0

XC = 0

XL = XC

$\sqrt{X{{}_{L}}^{2}+X{{}_{C}}^{2}}$

73. A common emitter transistor amplifier has a current fain of 50. If the load resistance is 4 kΩ and the input resistance is 500 Ω. The voltage gain on the amplifier is ....... [2070]

400

6.2

500

300

64. Watt per ampere is the unit of [2069]

electric potential

electric field intensity

electric power

electric energy

65. Two wires A and B of equal radii are drawn from the same material. Their lengths are 1m and 2m respectively. The resistivity of A is. [2069]

less than that of B

equal to that of B

more than that of B

depends upon the amount of current flowing in wires

66. When a capacitor is added in series in an LCR circuit, the impedance of the circuit [2069]

increase

decrease

remain unchanged

increases or decreases depending upon the frequency of a.c

67. A cell of emf X if connected across a resist of R. The potentional difference across the wire is measured as Y. The internal resistance of the cell should be [2069]

X - (Y/R)

(X-Y)R

(X-Y)R/X

(X-Y)R/Y

I there is