Exam 20: Electromagnetic Induction

A metal rod of length 2.0 m is moved at 6.0 m/s in a direction perpendicular to its length.A 5.0 m T magnetic field is perpendicular to both the rod and its velocity.What is the potential difference between the ends of the rod?

A generator is designed to produce a maximum emf of 170 V while rotating at 3200 rpm.The coils of the generator are circular with diameter 7.5 cm.Assuming the magnetic field in the generator is 0.075 T,what is the number of loops needed in the generator coil?

A transformer with a turns ratio of 20:1 is used to step down 120 vac,what is the peak voltage in the secondary?

A flat coil has a maximum flux 4.0 $\times$ 10^-3 T·m² through it as its area is perpendicular to a uniform magnetic field.When the coil is rotated 60 $^{\circ}$ (so that its normal makes a 60 $^{\circ}$ angle with the field),what is the flux through it?

A conducting rod is sliding on metal rails with velocity v.A magnetic field B is into the paper,the separation of the rails is L,and the resistance of the circuit is R.In what direction in the diagram is the current flowing in the resistor?

An LR circuit is prepared for an experiment,initially with its switch open.The time constant is that time after switch closure at which the current reaches what percentage of its final value

What number of turns on the secondary is needed to reduce the voltage from 120 V to 9.0 V if there are 40 turns on the primary of a step down transformer?

The north end of a bar magnet is pushed downward toward a wire loop in the plane of the paper.In which direction is the induced current,and which way is the induced magnetic field?

A 0.40 H inductor has a current that rises from zero to 3.0 A in 6.0 s.What is the average power required to accomplish this?

Induced emf in a straight segment of wire that passes through a magnetic field depends on all of the following,except:

The principle of operation that transformers depend upon is the induction of current in the secondary windings due to:

A 1.7 H inductor has a current of 6.6 A flowing through it.The current reduces to 3.3 A over a period of 1.6 s.What is the average power the inductor supplies to the circuit as the current reduces?

Reducing the magnetic field to 71% of its previous value changes the magnetic energy density in the field to _______% of its original value.

A transformer has 200 turns on its primary and 12 turns on its secondary.If the input voltage is 2000 V,what is the output voltage?

After the switch is closed in a series LR circuit,what is the current when a time equal to four time constants has elapsed?

If the number of turns on the transformer input is greater than the number on the output,then the transformer

A solenoid of length 4.00 cm and cross-sectional area 2.00 cm² has 80 turns.What is its self-inductance?

Eddy current in conductors

A series LR circuit includes a 9.0 V battery,a resistance of 0.50 $\Omega$ ,and an inductance of 0.80 H.What is the current 2.0 s after the switch is closed?

A copper pipe is held vertically and a magnet is dropped down the pipe.The magnet is oriented with the north pole down.What direction do the Eddy currents flow as viewed from above the pipe? If copper bar of approximately the same size and weight is dropped down the tube will it fall faster or slower?