Free GRE Physics Test Exam Questions and Answers

Two objects sliding on a frictionless surface, as represented above, collide and stick together. How much kinetic energy is converted to heat during the collision?

• AA. 1/9 J
• BB. 1/6 J
• CC. 1/2 J
• DD. 3/4 J
• EE. 5/6 J

Two simple pendulums A and B consist of identical masses suspended from strings of length L_A and L_B, respectively. The two pendulums oscillate in equal gravitational fields. If the period of pendulum B is twice the period of pendulum A, which of the following is true of the lengths of the two pendulums?

• AA. L_B = (1/4)L_A
• BB. L_B = (1/2)L_A
• CC. L_B = L_A
• DD. L_B = 2L_A
• EE. L_B = 4L_A

For the circuit shown in the figure above, what is the current i through the 2 Ω resistor?

• AA. 2 A
• BB. 4 A
• CC. 5 A
• DD. 10 A
• EE. 20 A

By definition, the electric displacement current through a surface S is proportional to the

• AA. magnetic flux through S
• BB. rate of change of the magnetic flux through S
• CC. time integral of the magnetic flux through S
• DD. electric flux through S
• EE. rate of change of the electric flux through S

The electric field of a plane electromagnetic wave of wave number k and angular frequency ω is given by E = E₀(e_x + e_y) sin(kz − ωt). Which of the following gives the direction of the associated magnetic field B?

• AA. e_z
• BB. −e_x + e_y
• CC. −e_x − e_y
• DD. e_x − e_z
• EE. e_y − e_z

Which of the following is true about any system that undergoes a reversible thermodynamic process?

• AA. There are no changes in the internal energy of the system.
• BB. The temperature of the system remains constant during the process.
• CC. The entropy of the system and its environment remains unchanged.
• DD. The entropy of the system and its environment must increase.
• EE. The net work done by the system is zero.

For which of the following thermodynamic processes is the increase in the internal energy of an ideal gas equal to the heat added to the gas?

• AA. Constant temperature
• BB. Constant volume
• CC. Constant pressure
• DD. Adiabatic
• EE. Cyclic

Light of variable frequency ν shines on the metal surface of a photoelectric tube. Einstein’s theory of the photoelectric effect predicts that the

• AA. work function of the metal is proportional to the frequency
• BB. work function of the metal is proportional to the wavelength
• CC. current in the tube is a linear function of the wavelength
• DD. potential difference necessary to stop the emitted electrons is a linear function of the frequency above the threshold frequency
• EE. potential difference necessary to stop the emitted electrons is equal to the work function

Characteristic X rays, appearing as sharp lines on a continuous background, are produced when high-energy electrons bombard a metal target. Which of the following processes results in the characteristic X rays?

• AA. Electrons producing Čerenkov radiation
• BB. Electrons colliding with phonons in the metal
• CC. Electrons filling inner shell vacancies that are created in the metal atoms
• DD. Electrons combining with protons to form neutrons
• EE. Electrons undergoing Coulomb scattering with nuclei

A single-electron atom has the electron in the ℓ = 2 state. The number of allowed values of the quantum number m_ℓ is

• AA. 1
• BB. 2
• CC. 3
• DD. 4
• EE. 5