UCSD Faraday Law of Induction Lenz’s Law Ac Current and Applications Questions


please follow the instruction on the pdf and the you are good to start. Objective: To study Faraday’s law of induction, Lenz’s law, AC current, and

Student’s name: _________________________ Grade: _______
Objective: To study Faraday’s law of induction, Lenz’s law, AC current, and
Theory: Refer to chapters 30 & 31 of Resnik and Halliday
The following picture shows a conducting loop connected to a sensitive ammeter.
There is no current in the circuit because there is no battery or other source of emf
included. However, if we move a bar magnet toward the loop, a current suddenly
appears in the circuit. The current disappears when the magnet stops. If we move
the magnet away, a current again suddenly appears, but now in the opposite
The current produced in the loop is called an induced current.
The work done per unit charge to produce that current is called induced emf.
The process to create induced current and induced emf is called induction.
Faraday’s law of induction:
If the magnetic flux through an area bounded by a closed conducting loop
changes with time, a current and an emf are produced in the loop. The induced
emf is:
Lenz’s law: An induced current has a direction such that the magnetic field due to
the current opposes the change in the magnetic flux that induces the current.
The induced emf has the same direction as the induced current.
The flux is changing in the following ways:
– The magnetic field through the loop changes (increases or decreases)
– The loop changes in area or angle
– The loop moves into or out of a magnetic field
AC current: is an electric current which periodically reverses direction and
changes its magnitude continuously with time in contrast to direct current which
flows only in one direction.
Alternating current is the form in which electric power is delivered to businesses
and residences, and it is the form of electric energy that consumers typically use
when they plug kitchen appliances, televisions, fans and electric lamps into a wall
Generators: A generator is a device that transforms mechanical energy into
electric energy.
(15 points)
Question 1: (3 points)
There are two loops as follows. The upper loop has a battery and a switch that has
been closed for a long time. How does the lower loop respond when the switch is
opened in the upper loop? Redraw the photo to support your answer.
Question 2: (3 points)
Two coils wrapped side by side on a cylinder as follows. When the switch for coil
1 is closed, what happens in coil 2? Redraw the photo.
Question 3: (3 points)
The long solenoid S shown in cross section as follows has n = 220 turns/cm and
carry a current I = 1.5 A. At its center we place a 130-turn closely packed coil C of
diameter d = 2.1 cm. The current in the solenoid is reduced to zero at a steady rate
in 25 ms. What is the magnitude of the emf that is induced in coil C while the
current in the solenoid is changing?
(𝑔𝑖𝑣𝑒𝑛: 𝜇𝑜 = 4𝜋. 10−7
𝑎𝑛𝑑 𝛷 = 𝐵. 𝐴)
Question 4: (3 points)
Compare self induction and mutual induction (similarities and differences).
Question 5: (3 points)
Open the DC generator simulation

Click “StepByStep” button. Explain in detail how the generator works and explain
the shape of the graph of voltage vs. time (for 4 steps).

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