ECAT Pre Engineering Physics Chapter 12 MCQ Test With Answer

A medium of dielectric constant 'K' is introduced between the plates of parallel plate condenser. As a result its capcitance

• Increase k time A
• Decreases k times B
• Decreases 1/K times C
• Remains unchanged D

An alpha particle is accelerated through a potential difference of 10⁶volt. Its kinetic energy will be

• 1 MeV A
• 2 MeV B
• 4 MeV C
• 8 MeV 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

The unit of intensity of electric field is

• newton/coluomb A
• jule/coluomb B
• volt x metre C
• newton/metre D

The SI unit of capacitance is

• Farad A
• Henry B
• Ohm C
• Volt D

In Pakistan electricity is supplied for domestic use at 220 V, it is supplied at 110 V in USA. If the resistance of a 60 W bulb for use in Pakistan is R, the resistance of a 60 W bulb for use in USA will be

• 2 R A
• R/4 B
• R/2 C
• R D

Electric potential of earth is taken to be zero because the earth is good

• Semiconductor A
• Conductor B
• Insulator C
• Dielectric D

• 5μF A
• 10μF B
• 3μF C
• 6μF D

A cube of metal is given a positive charge Q. For the above system, which of the following statements is true?

• Electric potential at the surface of the cube is zero A
• Electric potential within the cube is zero B
• Electric filed is normal to the surface of the cube C
• Electric filed varies within the cube D

The charge per unit time through any cross-section of a conductor is called

• capacitance A
• electric power B
• current C
• potential difference D

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

• 64 W A
• 80 W B
• 100 W C
• 125 W D

The SI unit of current is

• watt A
• coulomb B
• volt C
• ampere D

The current through a metallic conductor is due to the motion of

• protons A
• neutrons B
• electrons C
• free electrons 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 conventional current in a circuit is defined as " current which passes from a point at higher potential to a point at lower potential as if it represent a movement of

• negative charges A
• positive charges B
• protons C
• electrons D

The unit of resistance is

• volt A
• ampere B
• ohm C
• coat D

In bringing an electron towards another electron, electrostatic potential energy of system

• Decreases A
• Increases B
• Remains uncharged C
• Becomes zero D

The electric intensity at infinite distance from the point charge will be

• Infinite A
• Positive B
• Zero C
• Negative D

A wire is bent into a ring of radius R is given a charge q. The magnitude of the electrical field at the centre of the ring is

• Two A
• 1/2 B
• Zero C
• 3/2 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

The capacity of a parallel plat capacitor depends on the

• Type to metal used A
• Thickness of plates B
• Potential applied across the plates C
• Separation between the plates D

The fractional change in resistance per kelvin is known as

• temperature coefficient A
• resistance coefficient B
• super temperature C
• critical temperature D

Battery is charged in motor cars, which is based on

• Chemical effect A
• Magnetic effect B
• Electric effect C
• None D

Ohm established a relation between

• voltage and resistance A
• voltage and charge B
• voltage and current C
• voltage resistance and charge D

A one microfarad capacitor of a TV is subjected to 4000 V potential difference. The energy stored in capacitor is

• 8 J A
• 16 J B
• 4 x 10^-3J C
• 2 x 10^-3J D

The unit of conductance is

• ohm A
• meter B
• mho C
• ohm-meter D

A parallel plate capacitor is first charged and then a dielectric slab is introduced between the plates. The quantity that remains unchanged is

• Charge Q A
• Potential V B
• Capacity C
• Energy U D

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?

• 60 W bulb A
• 100 W bulb B
• Both equally C
• None of these D

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

• Copper A
• Al B
• Diode C
• None D

A proton is about 1840 times heavier than an electron. When it is accelerated by a potential difference of 1 KV, its kinetic energy will be

• 1840 KeV A
• 1/1840 KeV B
• 1 KeV C
• 920 KeV D