Session 23: Inductance and
RL Circuits 1
Supplemental Instruction
Iowa State University
Leader:
Course:
Instructor:
Date:
Garrett Schieber
Phys 222
Dr. Al-Saqer
10/27/14
1) Two coils have mutual inductance of M= 3.25×10−4 H. The current I1 in the first coil
increases at a uniform rate of 860 A/s. (Book 30.1)
a) What is the magnitude of the induced emf in the second coil?
b) Suppose that the current described is in the second coil rather than the first. What is the
magnitude of the induced emf in the first coil?
2) The inductor in the figure has inductance 0.260 H and carries a current in the direction shown
that is decreasing at a uniform rate, di/dt= - 1.80×10−2 A/s. Find the self-inducted emf. Which
end of the inductor is at a higher potential? (Book 30.9)
3) A solenoidal coil with 26 turns of wire is wound tightly around another coil with 330 turns.
The inner solenoid is 23.0 cm long and has a diameter of 2.30 cm. At a certain time, the
current in the inner solenoid is 0.130 A and is increasing at a rate of 1700 A/s. (Book 30.4)
a) For this time, calculate the average magnetic flux through each turn of the inner
solenoid.
b) For this time, calculate the mutual inductance of the two solenoids;
c) For this time, calculate the emf induced in the outer solenoid by the changing current in
the inner solenoid
Supplemental Instruction
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4) A 15.0 ohm resistor and a coil are connected in series with a 6.30-V battery with negligible
internal resistance and a closed switch. (Book 30.20)
a) At 2.00 ms after the switch is opened the current has decayed to 0.210 A. Calculate the
inductance of the coil.
b) Calculate the time constant of the circuit.
c) How long after the switch is opened will the current reach 1.00% of its original value?
5) At the instant when the current in an inductor is increasing at a rate of 6.45×10−2 A/s, the
magnitude of the self-induced emf is 1.65×10−2 V. What is the inductance of the inductor If
the inductor is a solenoid with 405 turns, what is the average magnetic flux through each turn
when the current is 0.725 A? (Book 30.7)