ECAT Pre Engineering Physics Chapter 12 MCQ Test With Answer

The relation between the charge Q of a parallel plate capacitor and the P.D between its plates is

• Q=V/C A
• Q=C/V B
• Q=1/2CV C
• Q=CV 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

The substances whose resistance decreases with the increase in temperature these substances have coefficient of

• positive temperature A
• negative temperature B
• absolute temperature C
• zero temperature 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 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

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

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

• Vaccum A
• Air B
• Glass C
• Water 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

Current provided by a battery is maximum when

• Internal resistance equal to external resistance A
• Internal resistance is greater than external resistance B
• Internal resistance is less then external resistance C
• None of these D

The SI unit of current is

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

The SI unit of capacitance is

• Farad A
• Henry B
• Ohm C
• Volt D

What is the current is a 2 x 10⁶ohm resistor having a potential difference of 2 x 10³volts?

• 10^-1A A
• 10^-2A B
• 10^-4A C
• 1 mA D

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

• protons A
• neutrons B
• electrons C
• free electrons D

The SI unit of electric field intensity is

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

An electron of charge e coulomb passes through a potential difference of V volts its energy in joules will be

• V/e A
• eV B
• e/V C
• V D

Resistance of a conductor depends upon

• the quantity of current passing through it A
• the voltage applied between its end B
• its dimensions, physical state and nature of its material C
• all of the above D

The electric field due to an infinite long thin wire at a distance R varies as

• 1/R A
• 1/R² B
• R C
• R² D

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

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

Two point charges A and B separated by a distance R attract each other with a force of 12 x 10^-3N. The force between A and B when the charges on them are doubled and distance is halved

• 1.92 N A
• 19.2 N B
• 12 N C
• 0.192 N D

If the resistance of 2 ohm and 4 ohm are connected in parallel, the equivalent resistance will be

• 6 ohm A
• 4 ohm B
• zero ohm C
• 1.33 ohm 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

Electron volt is the unit of.

• Potential difference A
• Energy B
• Resistance C
• Capacitance 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

A capacitor is charged with a battery and then it is disconnected. A slab of dielectric is now inserted between the plates, then

• The charge in the plates reduces and potential difference increase A
• Potential difference between the plates increase, stored energy decreases and charge remains the same B
• Potential difference between the plates decreases and charge remains unchanged C
• None of the above D

A hollow insulated conduction sphere is given a positive charge of 10μC. What will be the electric field at the centre of the sphere if its radius is 2 meters?

• Zero A
• 5μC m^-2 B
• 20μC m^-2 C
• 8μC m^-2 D

A conducting wire is drawn to double its length. Final resistivity of the material will be

• Double of the original one A
• Half of the original one B
• One fourth of the original one C
• Same as original one D

The potential difference across each resistance in series combination is

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

The dot product of electric field intensity E and vector area A is called

• Electric potential A
• Electric flux B
• Electric field C
• Magnetic field D

• 5μF A
• 10μF B
• 3μF C
• 6μF D

The unit of conductance is

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