ECAT Pre Engineering Physics Chapter 12 MCQ Test With Answer

The nature of capacity of electrostatic capacitor depends on

• Shape A
• Size B
• Thickness of plates C
• Area 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

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

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 SI unit of permitivity is

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

Heating effect caused by an electric circuit is written

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

Some charge is being given to a conductor. Then its potential

• Is maximum at surface A
• Is maximum at centre B
• Is remain same throughout the conductor C
• Is maximum somewhere between surface and centre D

The earth's potential is taken as

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

Three resistance 500,500 and 50 ohms are connected in series across 555 volts mains. The current flowing through them will be

• 0.52 A A
• 1 mA B
• 0.7 mA C
• 1.4 A D

The resistance of a conductor does not depend on its

• mass A
• resistivity B
• length C
• cross-sectional area D

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

• parabola A
• straight line B
• hyper bola C
• ellipse D

A 10 F capacitor is charged to a potential difference of 50 V and is connected to another uncharged capacitor in parallel. Now the common potential difference becomes 20 volt.The capacitance of second capacitor is

• 10μF A
• 20μF B
• 30μF C
• 15μF D

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

• 1310 W A
• 670 W B
• 810 W C
• 1210 W D

Capacitance of two or more capacitors

• Increases in series combination A
• Increases in parallel combination B
• Remains unchanged C
• None of the above D

Electric generators which convert mechanical energy into

• solar energy A
• thermal energy B
• kinetic energy C
• electrical energy 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

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

A wire of radius r has resistance R. If it is stretched to a wire of r/2 radius, then the resistance becomes

• 2R A
• 4R B
• 16R C
• Zero 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

Thermocouple is an arrangement of two different metals

• To convert heat energy in to electrical energy A
• To produce more heat B
• To convert heat energy into chemical energy C
• To convert electric energy in to heat energy 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

Which one of the following is the unit of electric field intensity

• JC^-1 A
• Vm^-1 B
• Cm^-1 C
• CJ^-1 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

Ohm's law states that

• The current through a resistor is directly proportional to the applied voltage A
• The voltage across a resistor is directly proportional to the current passing through it B
• Resistance is the constant of proportionality between the voltage and current C
• all of these D

Surface density of charge is defined as

• Charge per unit volume A
• Charge per unit length B
• Charge per unit area C
• Charge per unit mass D

In a voltmeter the conduction takes place due to

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