Physics Mcqs

A piece of copper and a piece of germanium are cooled from the room temperature down to 77 K.A. The resistance of each of them increases.
B. The resistance of each of them decreases.
C. The resistance of copper decreases and that of germanium increases.
D. The resistance of copper increases and that of germanium decreases

 

Two parallel beams of positrons moving in the same direction will________?A. repel each other
B. not interact with each other
C. attract each other
D. be deflected normal to the plane containing the two beams.

 

An emf of 5 volt is produced by a self inductance, when the current changes at a steady rate from 3 to 2 ampere in 1 millisecond. The value of self inductance is_______?A. zero
B. 5 H
C. 5000 H
D. 5 mH

 

The core of a transformer is laminated to reduce energy losses due to__________?A. Eddy currents
B. Hysteresis
C. Resistance in winding
D. None of these

 

Electric current in a solid metal conductor is caused by the movement of what ?

A. Protons
B. Electrons
C. Metal atoms
D. Metal ions

Electric current in a solid metal conductor is caused by the movement of electric charge. An electric current is the flow of electric charge. An electron current, the flow of electrons, contributes to an electric current since the electron ‘carries’ negative electric charge.

A force On particle is conservative if:________?

A. It’s works equals the change in the kinetic energy of the particle.
B. It’s obeys Newton’s second law
C. It’s obeys Newton’s third law
D. It work depends on the end points of every motion, not on the path between.

A conservative force is a force with the property that the total work done in moving a particle between two points is independent of the path taken.

A Stone thrown from the top of a tall building follows a path that is:

A. Circular
B. Made of two straight line segments
C. Hyperbolic
D. Parabolic

The speed of light will be minimum while passing through ?A. Vaccum
B. Glass
C. Water
D. Air

The speed of light will be minimum while passing through which of the following mediums? Notes: Light travels at approximately 300,000 kilometers per second in a vacuum, which has a refractive index of 1.0, but it slows down to 225,000 kilometers per second in water and 200,000 kilometers per second in glass.

 

The efficiency of the Carnot engine working between 150°C and 50°C is__________?

A. 50%
B. 100%
C. 23.6%
D. 29.4%

Explain: formula
n% = (1- T2/T1) ×100%
T1= 273+150= 423K
T2:273+50= 323K
n% = (1- 323/423)×100%
n% = 0.236×100% = 23.6% Correct