ECAT Pre General Science 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

The unit of resistance is

• volt A
• ampere B
• ohm C
• coat 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 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

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

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

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

At any point on the right bisector of the line joining two equal and opposite charges

• At electric field is zero A
• The electric potential is zero B
• The electric potential decreases with increasing distance from the centre C
• The electric field is perpendicular to the line joining the charges D

If an electron of charge 'e' is accelerated through a potential difference V., it will acquire energy

• Ve A
• V/e B
• e/V C
• 2Ve D

A point charge Q is placed at the mid-point of a line joining two charges. 4q and q. if the net force on charge q is zero. then Q must be equal to

• -q A
• +q B
• -2q C
• +4q D

The electric lines of force are

• Imaginary A
• Physically existing everywhere B
• Physically existing near the charge C
• All of the above D

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

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

In case of a parallel plate capacitor if the plate separation is doubled and plate area is halved, the capacitance becomes

• Four-fold A
• One-half B
• One-fourth C
• Zero D

The concept of field theory was put forward by

• Franklin A
• Kepler B
• Oersted C
• Michael Faraday D

The fractional change in resistance per kelvin is known as

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

An electric charge at rest is

• Only an electric field A
• Only a magnetic field B
• Both electric and magnetic fields C
• None of the above D

The electrode connected with the positive terminal of the current source is called

• cathode A
• anode B
• electrolyte C
• position 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

The resistance of 20 cm long wire is 10Ω. When the length is changed to 40 cm. The new resistance is

• 10Ω A
• 20Ω B
• 30Ω C
• 40Ω D

The electric potential at the surface of an atomic nucleus (Z = 50) of radius 9.0 x 10^-15 is

• 9 x 10⁵V A
• 9 V B
• 8 x 10⁶V C
• 80 V D

• 5μF A
• 10μF B
• 3μF C
• 6μF D

The electric intensity outside the two oppositely charged parallel metal plates is

• Maximum A
• Minimum B
• Zero C
• Infinite 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

Capacitance of two or more capacitors

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

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

The unit of resistivity is

• ohm A
• ohm-m² B
• ohm-meter C
• ohm-m^-1 D

Free electrons are

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

10⁶electrons are moving through a wire per second, the current developed is

• 1.6 x 10^-19 A
• 1 A B
• 1.6 x 10^-15 A C
• 10⁶A D