ECAT Pre Engineering Physics Chapter 12 MCQ Test With Answer

One coulomb of charge is created by

• 10 electrons A
• 1.6 x 10^-19electrons B
• 6.25 x 10¹⁸electrons C
• 6.25 x 10²¹electrons D

At any point on the right bisector of the line joining two equal and opposite charges

• At electric field is zero A
• The electric potential is zero B
• The electric potential decreases with increasing distance from the centre C
• The electric field is perpendicular to the line joining the charges D

One electron volt is equal to

• 1.6 x 1019eV A
• 6.25 x 1018 eV B
• 1.6 x 1018 eV C
• 6.25 x 1019eV D

Cause of heat production in a current carrying conductor is

• Collisions of free electrons with one another A
• High drift speed of free electrons B
• Collisions of free electrons with atoms or ions of conductor C
• High resistance value D

A metal plate of thickness half the separation between the capacitor plates of capacitance C is inserted. The new capacitance is

• C A
• C/2 B
• Zero C
• 2C D

A piece of fuse wire melts when a current of 15 ampere flows through it. With this current. If it dissipates 22.5 W, the resistance of fuse wire will be

• Zero A
• 10Ω B
• 1Ω C
• 0.10Ω D

• 5μF A
• 10μF B
• 3μF C
• 6μF D

The electric field intensity at a point due to a point charge

• Falls off inversely as the distance A
• Falls off inversely as the square of distance B
• Remains unchanged with distance C
• Increase directly as square of distance D

If we increase the distance between two plates of the capacitor, the capacitance will

• Increase A
• Decrease B
• Remain same C
• First increase then decrease D

Heating effect caused by an electric circuit is written

• H = I²Rt A
• H = I²R B
• H = IR²t C
• H = IR² D

The powers of tow electric bulbs are 100 W and 200 W. Both of them are joined with 220 V mains. The ratio of resistances of their filaments will be

• 1 : 2 A
• 2 : 1 B
• 1 : 4 C
• 4 : 1 D

A (100 W , 200 W) bulb is connected to a 160 V power supply. The power consumption would be

• 64 W A
• 80 W B
• 100 W C
• 125 W D

In RC series circuit the time during which the capacitor acquires 0.63 times the equilibrium charge is called

• Time constant A
• Decay constant B
• None of these C
• All of above D

A sheet of aluminium foil of negligible thickness is introduced between the plates of a capacitor. The capacitance of the capacitor

• Increases A
• Decreases B
• Remain unchanged C
• Becomes infinite D

A certain charge liberates 0.8 g of oxygen. The same charge will liberate. how many g of silver?

• 108 g A
• 10.8 g B
• 0.8 g C
• 108/0.8 g D

If a charged spherical conductor of radius 10 cm has potential V at a point distance 5 cm from its centre, then the potential at a point distance 15 cm from the centre will be

• 1/3 V A
• 2/3 V B
• 3/2 V C
• 3V D

Resistance of a conductor is increased, the currant will

• Decrease A
• Increase B
• Remain the same C
• None of these D

In a charged capacitor the energy is stored in

• Both in positive and negative charges A
• Positive charges B
• The edges of the capacitor plates C
• The electric field between the plates D

The value of electrical constant of proportionality k is

• 9 x 10⁹Nm²C^-2 A
• 9 x 10^-9Nm²C^-2 B
• 9 x 10¹⁰Nm²C² C
• 9.85 x 10^-12N^-1C^-2 D

The potential difference across each resistance in series combination is

• same A
• different B
• zero C
• none of these D

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)

• Q/4πr² A
• 2Q/4πr² B
• Q.d C
• Zero D

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

• E=mg/q A
• E=q/mg B
• E=,g/q C
• E=qg/m D

In a voltmeter the conduction takes place due to

• Electrons only A
• Holes only B
• Electrons and holes C
• Electrons and ions D

The resistance of an incandescent lamp is

• Smaller when switched on A
• Greater when switched off B
• The same whether it is switch off or switch on C
• Greater when switched on D

The SI unit of permitivity is

• Nm²C² A
• N^-1m^-2C² B
• NmC² C
• Nm²C^-1 D

The electric intensity outside the two oppositely charged parallel metal plates is

• Maximum A
• Minimum B
• Zero C
• Infinite D

The SI unit of electric field intensity is

• CN^-1 A
• NC^-1or Vm^-1 B
• JC^-1 C
• AV^-1 D

Which one of the following has larger value of relative permitivity E_rat room temperature?

• Vaccum A
• Air B
• Glass C
• Water D

The SI unit of electric flux is

• Weber A
• Nm²C^-1 B
• NmC^-1 C
• Nm^-2C D

The relation V = IR represents

• Ampere law A
• Faraday's law B
• Ohm's law C
• Len's law D