Chapter 23 Flashcards
(18 cards)
Faraday’s Experiment
A changing magnetic field can induce an emf, driving a current
Faraday’s Experiment
The switch in the primary circuit is closed, the secondary circuit measures a momentary current
The emf in the secondary circuit is induced by the changing magnetic field through the coil
Magnetic Flux
Changing magnetic flux creates electric field
Magnetic Flux
Proportional to number of lines through loop
Magnet TOWARDS loop
current (-)
Magnet AWAY loop
OPPOSITE current (+)
Faraday’s Law
If a circuit contains N loops and the magnetic flux changes by ∆ΦB during the interval Δt, the average emf is induced
Lenz’s Law
The current caused by the induced emf travels in the direction that creates a magnetic field with flux opposing the change in the original flux through the circuit
A bar magnet is falling toward the center of a loop of wire, with the north pole oriented downward. Viewed from the same side of the loop as the magnet, as the north pole approaches the loop, what is the direction of the induced current?
Counterclockwise
Two circular loops are side by side and lie in the xy-plane. A switch is closed, starting a counterclockwise current in the left-hand loop, as viewed from a point on the positive z-axis passing through the center of the loop. Which of the following statements is true of the right-hand loop?
An induced current moves counterclockwise
You intend to move a rectangular loop of wire into a region of uniform magnetic field at a given speed so as to induce an emf in the loop. The plane of the loop must remain perpendicular to the magnetic field lines. In which orientation should you hold the loop while you move it into the region with the magnetic field to generate the largest emf?
With SHORT DIMENSION of the loop PARALLEL to the velocity vector
Motor (BACK EMF)
Electrical energy to mechanical energy
changing magnetic flux through it induces an emf that acts to reduce the current in the coil
Generator (reverse)
Current supplied to loop and magnetic torque creates rotation
Self-inductance
Changing flux through the circuit arises from the circuit itself
.
Inductance
Measure of opposition to rate of change of current
The switch in the circuit shown in the figure below is closed, and the lightbulb glows steadily. The inductor is a simple solenoid. An iron rod is inserted into the interior of the solenoid, increasing the magnitude of the magnetic field in the solenoid. As the rod is inserted, the brightness of the lightbulb
Decreases
Self-induced emf
Prevents a battery from instantaneously establishing current in a circuit.
The battery has to do work to produce a current.
This work goes into energy that will be stored in the inductor in its magnetic
For which of the following is an emf induced
A conducting rod is pulled on conducting rails that are placed in a uniform magnetic field directed into the page
A conducting loop rotates in a uniform magnetic field directed into the page
