ECAT Pre Engineering Physics Chapter 12 MCQ Test With Answer

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

In a Milikian's oil drop experiment the charge on an oil drop is calculated to be 6.35 x 10^-19C. The number of excess electrons on the drop is

• 3.9 A
• 4 B
• 4.2 C
• 6 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

For two resistance wires joined in parallel, the resultant resistance is 6/5 ohm. When one of the resistance wire breaks, the effective resistance becomes 2 ohm. The resistance of the broken wire is

• 3/5 ohm A
• 2 ohm B
• 6/5 ohm C
• 3 ohm D

The graphical representation of ohm's law is

• hyperbola A
• straight line B
• ellipse C
• parabola D

A uniform resistance wire of Length L and diameter d has a resistance R. Another wire of same material has length, 4L and diameter 2d, the resistance will be

• 2 R A
• R B
• R/2 C
• R/4 D

The SI unit of capacitance is

• Farad A
• Henry B
• Ohm C
• Volt 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

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

When an electron is accelerated through a P.D. of an one volt, it will acquire energy equal to

• One joule A
• One erg B
• One electron volt C
• None of these 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

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

The speed of randomly moving electrons depends upon

• pressure A
• volume B
• temperature C
• mass D

The SI unit of electric flux is

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

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

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

• 5μF A
• 10μF B
• 3μF C
• 6μF 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

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

Physicist George Simon ohm was a

• German physical A
• French physicist B
• Chinese physicist C
• Russian physicist D

A capacitor of capacity 1μF is charged to 1 KV. The energy stored in J

• 5 A
• 0.5 B
• 0.005 C
• 50 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

Coulomb force, when any material medium is placed between two charges

• Increases A
• Decreases B
• Remain unchanged C
• None of these 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

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 earth's potential is taken as

• Negative A
• Positive B
• Zero C
• Infinite 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

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

• Vaccum A
• Air B
• Glass C
• Water 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

The charge carriers in gases are

• electrons A
• ions B
• protons C
• ions and electrons D