Thank God It's Faraday!
Through an Objective Lenz
Induction to the APC Hall of Fame
L/C on my RL
Physics Finalé
100
A magnetic field of magnitude 4.0T is directed at an angle of 30° to the plane of a rectangular loop of area 5.0m2, as shown above. What is the magnetic flux through the loop?
10 T⋅m2
100
Which of the following is found using Lenz's law?
i. Induced emf
ii. Induced current
iii. Direction of induced emf
iv. Direction of alternating current
Direction of induced emf
100
A circuit contains two inductors of 6.0 mH inductance in series placed in parallel with an inductor of 8.0 mH inductance. After one of the 6.0 mH inductors burns out, the repair person wants to replace all three inductors with one inductor of equivalent inductance. Assuming inductors combine in series and parallel the same way resistors do, what inductance should she use?
4.8 mH
100
An inductor and two resistors are connected to an ideal battery, as shown in the figure below. What is the time constant for the circuit?
1.0 μs
100
In the beginning of the course, you took a questionnaire claiming to be the most this.
What is serious?
200
A 40-turn circular coil (radius = 4.0 cm, resistance = 0.20 Ω) is placed in a uniform magnetic field directed perpendicular to the coil. The magnitude of the magnetic field varies with time as given by B = 50 sin(10πt) mT where t is measured in s. What is the magnitude of the induced current in the coil at 0.10 s?
1.6 A
200
A wire loop carrying no current is placed near another very long straight wire carrying current I. The loop is then moved directly away from the straight wire at a constant speed.
In which direction will the current induced in the small wire loop flow? 
Clockwise
200
Express a henry in terms of base units.
Kilogram meter squared per second squared per ampere squared (kg m2 s-2 A-2)
200
After the switch is closed in the circuit above, the current in the circuit is given by i=I(1−e−t/τ), where I and τ are constants. What is the value of I?
0.001 A
200
The day I forgot to input your Quiz 2 grades before returning them to you was dubbed this name.
What is Wacky Wednesday?
300
An emf of 20 V is induced around a metal ring by increasing a uniform magnetic field at a constant rate from zero to a final magnitude of 1.0 × 10–2 T throughout the region enclosed by the ring. The field direction is perpendicular to the plane of the ring.
If the area enclosed by the ring is 4.0 × 10–3 m2 , what is the time interval during which the field is increased?
2.0 μs
300
A metal wire of resistance 10 Ω is bent into a circular hoop of radius 0.10 meter and placed in a uniform magnetic field, as shown in Figure 1 above. The magnetic field strength B as a function of time is shown in Figure 2, where positive refers to a magnetic field directed out of the page. What are the magnitude and direction of the current induced in the ring at time t = 6 s?
0.42 mA, Counterclockwise
300
A variable voltage source is connected to an inductor of inductance L. The voltage V as a function of time t is given by the equation V(t) = βt2 , where β is a constant in units of V/s2. The current in the inductor at time t = 0 is zero. What is the equation for the magnitude of the current in the inductor as a function of time?
I(t)=β/(3L)t^3
300
There is no current in the circuit shown in the figure below until the switch is closed. What is the current through the 20-Ω resistor the instant after the switch is closed, and the current through the 20-Ω resistor after the switch has been closed a long time?
5 A right after and 15 A after a long time
300
The exam on this topic in Mechanics had the lowest average grade.
What is momentum?
400
A 120-turn coil of radius 1.8 cm and resistance 5.3 Ω is coaxial with a solenoid of 220 turns/cm and diameter 3.2 cm. The solenoid current drops from 1.5 A to zero in time interval Δt = 25 ms. What current is induced in the coil during Δt?
0.030 A
400
A bar moves on two frictionless rails, as shown, in a region where the magnetic field is uniform and into the paper. What is the direction of the magnetic force on the moving bar?
Left
400
What is the inductance of a series RL circuit in which R = 1.0 KΩ if the current increases to one-third of its final value in 30 µs?
74 mH
400
Before the switch is closed in the figure, the potential across the capacitor is 200 V. At some instant after the switch is closed, the instantaneous current is 0.70 A. What is the energy in the capacitor at this instant? 
31 mJ
400
This German physicist is known for sporting a smoker's cap.
Who is Carl Gauss?
500
A loop antenna of area 2.00 cm2 and resistance 5.21 μΩ is perpendicular to a uniform magnetic field of magnitude 17.0 μT. The field magnitude drops to zero in 2.96 ms. How much thermal energy is produced in the loop by the change in field?
7.50 x 10-10 J
500
A bar magnet is dropped from above and falls through the loop of wire shown below. The north pole of the bar magnet points downward towards the page as it falls. What is the direction of the induced current in the ring as the bar magnet passes by? Hint: current may change.
The current in the loop flows first in a counterclockwise, then in a clockwise direction.
500
A long solenoid (n = 1500 turns/m) has an area of 0.40 m2 and a current given by I = (4.0 + 3.0t2) A, where t is in seconds. A flat circular coil (N = 300 turns) with a cross-sectional area of 0.15 m2 is inside and coaxial with the solenoid. What is the magnitude of the emf induced in the coil at t = 2.0 s?
1.0 V
500
A coil is connected in series with a 10.0 kΩ resistor. An ideal 50.0 V battery is applied across the two devices, and the current reaches a value of 2.00 mA after 5.00 ms. Find the inductance of the coil.
97.9 mH
500
In the UK, Never Gonna Give You Up was the biggest single of 1987, staying at #1 for this many weeks.
What is 5?