ECAT Pre Engineering Physics Chapter 12 MCQ Test With Answer

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

A charge of 0.1 c accelerated through a potential difference of 1000V acquires kinetic energy

• 200 J A
• 100 J B
• 1000 J C
• 400 J D

Three resistors of resistance R each are combined in various ways. Which of the following cannot be obtained?

• 3RΩ A
• 2R/4Ω B
• R/3Ω C
• 2R/3Ω D

• 5μF A
• 10μF B
• 3μF C
• 6μF D

Which of the following represents an electric current?

• C^-1 A
• CS^-1 B
• J.S^-1 C
• dynes^-1 D

A 60 W bulb operates on 220 V supply. The current flowing through the bulb is

• 11/3 A A
• 3 A B
• 3/11 A C
• 6 D

The relation V = IR represents

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

The resistance of the given conductor can be increased by

• Increasing the area A
• Changing resistivity B
• Decreasing the length C
• None of the above because change does not matter because in any case the volume remains the same D

The unit of resistance is

• volt A
• ampere B
• ohm C
• coat 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 energy required to charge a capacitor of 5μF by connecting D.C. source of 20 KV is

• 10 KJ A
• 5 KJ B
• 2 KJ C
• 1 KJ D

The liquid which conduct current is known as

• heating effect A
• chemical energy B
• electrolyte C
• ohm's law D

The SI unit of current is

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

The unit of conductance is

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

Battery is charged in motor cars, which is based on

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

A car battery has e.m.f 12 volt and internal resistance 5 x 10^-2ohm. If it draws 60 ampere current, the terminal voltage of the battery will be

• 5 volt A
• 3 volt B
• 15 volt C
• 9 volt D

The SI unit of capacitance is

• Farad A
• Henry B
• Ohm C
• Volt D

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

• R₁= 2R₂ A
• R₂= 2R₁ B
• R₂ = 4R₁ C
• R₁= 4R₂ D

Potentiometer is more sensitive than voltmeter, because

• Voltmeter has a very high resistance A
• Voltmeter has a very low resistance B
• Potentiometer does not draw any current from a source of unknown potential difference C
• Potentiometer is sensitive 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

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

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

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

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

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

• Increase four fold A
• Become one-fourth B
• Become one-half C
• Remains unchanged D

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

• 0.4 A A
• 11.4 A B
• 9.8 A C
• 10.6 A D

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

• 25 A
• 225 B
• 625 C
• 1250 D

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

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

Free electrons are

• tightly bound A
• fixed B
• loosely bound C
• tightly fixed D

A 50 volt battery is connected across 10 ohm resistor. The current is 4.5 A. The internal resistance of the battery is

• Zero A
• 0.5Ω B
• 1.1Ω C
• 5.0Ω D

In a voltmeter the conduction takes place due to

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