Waec Physics 2020 Past Questions and Answers

Question 31:

• WAEC 2020

An electron of mass m and charge e moves in a circular path in a magnetic field of flux density B. How long does it take to complete one orbit?

A. \(\frac{2me}{B\pi}\)
B. \(\frac{2B}{me\pi}\)
C. \(\frac{2\pi m}{Be}\)
D. \(\frac{Be}{2 \pi m}\)

Question 32:

• WAEC 2020

Which of the following statements about photoelectrons is correct?

A. A faint green light produces photoelectrons with less kinetic energy than a bright red light
B. A red light releases a smaller number of electrons than a green light
C. A faint green light produces photoelectrons with greater kinetic energy than a bright red light
D. A red light produces more photoelectrons than a green light

Question 33:

• WAEC 2020

The sketched graph above illustrates the heating curve of a 0.02kg of water. Determine the approximate value of the specific latent heat of vapourization of water

A. 2.25 x 10\(^6\) J kg\(^{-1}\)
B. 4.17 x 10\(^3\) J kg\(^{-1}\)
C. 2.00 x 10\(^3\) J kg\(^{-1}\)
D. 1.00 x 10\(^3\) J kg\(^{-1}\)

Question 34:

• WAEC 2020

In the hydraulic press, the force F applied is related to the diameter d of the cylinder by

A. F \(\alpha\) d\(^2\)
B. F \(\alpha\) d
C. F \(\alpha\) d\(^{-1}\)
D. F \(\alpha\) d\(^{-2}\)

Question 35:

• WAEC 2020

In an electric circuit, an inductor of inductance 0.5 H and resistance 50\(\Omega\) is connected to an alternating current source of frequency 60 Hz. Calculate the impedance of the circuit.

A. 50.0\(\Omega\)
B. 450.5 \(\Omega\)
C. 195.0 \(\Omega\)
D. 1950.1 \(\Omega\)