Question # 1

The excess (equal in number) of electrons that must be placed on each of two small spheres spaced 3 cm apart, with force of repulsion between the spheres to be 10^-19N, is

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25

225

625

1250

The concept of field theory was put forward by

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Franklin

Kepler

Oersted

Michael Faraday

The ratio of the gravitational force F_gto the electrostatic force F_ebetween two electrons at the same distance apart is approximately

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9.8

24 x 10¹⁹

24 x 10⁴²

24 x 10^-44

Surface density of charge is defined as

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Charge per unit volume

Charge per unit length

Charge per unit area

Charge per unit mass

If we plot graph between potential difference (V) and current (I) obeying ohm's law, it will give us

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parabola

straight line

hyper bola

ellipse

The thermistors are usually made of

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Metals with low temperature coefficient of resistivity

Metals with high temperature coefficient of resistivity

Metal oxides with high temperature coefficient of resistivity

Semi conducting materials having low temperature coefficient of resistivity

If electric and gravitational force on an electron in a uniform electric field will be

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E=mg/q

E=q/mg

E=,g/q

E=qg/m

The SI unit of capacitance is

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Farad

Henry

Ohm

Volt

A closed surface contains two equal and opposite charges. The net electric flux from the surface will be

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Negative

Positive

Infinite

Zero

Two electric bulbs of 200 W and 100 W have same voltage. If R₁and R₂be their resistance respectively then

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R₁= 2R₂

R₂= 2R₁

R₂=4R₁

R₁= 4R₂

The unit of resistance is

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volt

ampere

ohm

coat

In case of a parallel plate capacitor if the plate separation is doubled and plate area is halved, the capacitance becomes

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Four-fold

One-half

One-fourth

Zero

Current provided by a battery is maximum when

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Internal resistance equal to external resistance

Internal resistance is greater than external resistance

Internal resistance is less then external resistance

None of these

If the distance between the plates of a parallel plate condenser of capacity 10μF is doubled then new capacity will be

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5μF

20μF

10μF

15μF

If two bulbs one of 60 W and other of 100 W are connected in parallel, then which one of the following will flow more?

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60 W bulb

100 W bulb

Both equally

None of these

A uniform resistance wire of Length L and diameter d has a resistance R. Another wire of same material has length, 4L and diameter 2d, the resistance will be

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2 R

R

R/2

R/4

A condenser of capacity 50μF is charged to 10 V.The energy stored is

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1.25 x 10^-3J

3.75 x 10^-3J

2.5 x 10^-3J

5 x 10^-3J

A ten ohm electric heater operates on a 110 V line. Calculate the rate at which it develops heat in watts

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1310 W

670 W

810 W

1210 W

The liquid which conduct current is known as

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heating effect

chemical energy

electrolyte

ohm's law

If the length of the conductor is double and its cross sectional area is halved, its conductance will

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Increase four fold

Become one-fourth

Become one-half

Remains unchanged

In a building, there are 15 bulbs of 40 watts, 5 bulbs of 100 watts, 5 fans of 80 watts and a heater of 1 kilowatt. The voltage of the electric main is 220 volts. The minimum efficiency of the main fuse of the building will be

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0.4 A

11.4 A

9.8 A

10.6 A

The electric flux from a closed surface

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Is independent of the shape of the surface

Depends on the charge enclosed by the surface

Both a and b

None of the above

A charge Q is divided into two parts q and Q - q and separated by a distance R. The force of repulsion between them will be maximum when

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q = Q/4

q = Q/2

q = !

None of these

Potentiometer is more sensitive than voltmeter, because

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Voltmeter has a very high resistance

Voltmeter has a very low resistance

Potentiometer does not draw any current from a source of unknown potential difference

Potentiometer is sensitive

Ohm is the unit of

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current

capacitance

energy

resistance

The energy stored in a charge capacitor

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1/2CV²

1/2C²V

1/2C/V²

None of these

At ordinary temperature, an increase in temperature increases the conductivity of

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Conductor

Semiconductor

Insulator

Alloy

The electric lines of force are

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Imaginary

Physically existing everywhere

Physically existing near the charge

All of the above

A point charge A of charge +4μC and another B of charge -1μC are placed in air at a distance 1 m apart. Then the distance of the point on the line joining the charge B, where the resultant electric field is zero, is (in m)

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2

1

0.5

1.5

Which of the following does not obey ohm's law?

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Copper

Al

Diode

None

An electric dipole is at the centre of a hollow sphere of radius r. The total normal electric flux through the sphere is (here Q is the charge and d is the distance between the two charges of the dipole)

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Q/4πr²

2Q/4πr²

Q.d

Zero

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