INTERNATIONAL UNIVERSITY (IU) – VIETNAM NATIONAL UNIVERSITY - HCMC
FINAL EXAMINATION – CLASS
Student Name:_______________________Student ID:___________________
Date: June 2021
TEST 1
Duration: 2 days (from 10:15 AM 29th June to 10:15 AM 1st July 2021)
SUBJECT: PHYSICS 3
Chair of Department of Physics:
Lecturers: Phan Bảo Ngọc
Signature:
Signature:
Full name: Phan Bảo Ngọc
Instructions: Any submission with the same/identical solutions or explanations as those of other students in the exam will
get zero.
1/ (20 pts) An electron moves in a uniform magnetic field with a velocity of
𝑣⃗ = (2.0𝚤̂ + 4.0𝚥̂) × 10! m/s. The magnetic force acting in the electron is 12´10-14 N and along the
positive z-axis.
(a) Find the y component of the magnetic field if its x component is equal to zero. Sketch 𝐹⃗" ,
5⃗ in the Cartesian coordinate system Oxyz.
𝑣⃗, and 𝐵
(b) Can we use this magnetic field to boost the kinetic energy of the electron? Explain.
2/ (20 pts) The magnetic dipole moment of Earth is produced by charges flowing in the molten
outer core of Earth. If 𝜇#$%&' = 10() Am2, the radius of the circular path of charges r = 3500 km,
calculate the current produced by the charges.
3/ (20 pts) Three inductors L1, L2 and L3 are connected in parallel and separated by a large distance.
(a) Find the equivalent inductance of these three inductors.
(b) If these inductors are very close to each other, can we use the formula found in question (a)
to calculate the equivalent inductance? Explain.
4/ (20 pts) A loop of wire with area A is placed in a magnetic field 𝐵(𝑡 ) = 𝑡 ( − 3𝑡 + 2 (B in teslas
and t in seconds). Determine when the induced current in the loop changes its direction.
(Hint: Sketch the B versus t diagram to examine when B changes in direction and magnitude. You
could use an online graphing to examine)
+
5/ (20 pts) An alternating-current generator with 𝜀 (𝑡) = 7 sin𝜔𝑡 (𝑉) and 𝑖 (𝑡) = 𝑖* sin (𝜔𝑡 − ! )
drives a series RLC circuit. Find the potential difference (magnitude and sign) across the inductor
when the potential difference across the capacitor reaches its maximum positive value of +6 V.
(A phasor diagram should be included)
END OF QUESTION PAPER