pHysics 2 exm 3

A loose spiral spring carrying no current is hung from a ceiling. When a switch is thrown so that a current exists in the spring, do the coils

Move closer together

Amperes law

The total magnetic field circulating around the closed loop path is equal/proportional to the electric current passing though that path

ferromagnetism

A small number of substances exhibit strong magnetic effects called_____. Some examples of ferromagnetic substances are iron, cobalt, nickel, gadolinium, and dysprosium. These substances contain permanent atomic magnetic moments that tend to align parallel to each other even in a weak external magnetic field. Th

Paramagnetic substances

have a weak magnetism resulting from the presence of atoms (or ions) that have permanent magnetic moments. These moments interact only weakly with one another and are randomly oriented in the absence of an external magnetic field.

Consider a solenoid that is very long compared with its radius. Of the following choices, what is the most effective way to increase the magnetic field in the interior of the solenoid?

overwrap the entire solenoid with an additional layer of current-carrying wire

What creates a magnetic field?

a moving object with electric charge and a stationary conductor carrying electric current

What happens to the field if the radius is doubled?

it is unchanged, it depends on the turns and current

What happens to the magnitude of the magnetic field inside a long solenoid if the current is doubled?

It become twice as large

What happens to the field if instead the length of the solenoid is doubled, with the number of turns remaining the same?

n=N/2l  which is 1/2. the original formula is N/length

An identical particle enters the field, with vector v perpendicular to vector B , but with a higher speed than the first particle.

A circular loop of wire is held in a uniform magnetic field, with the plane of the loop perpendicular to the field lines. Which of the following will not cause a current to be induced in the loop?

Keeping orientation fixed and moving it along the field lines → B, A, and θ all stay constant → flux doesn’t change → no current induced ❌

Crushing the loop changes the area and flux which causes the current to be induced

Rotating the loop about an axis perpendicular to the field lines changes the angle.

Pulling the loop out of the field changes B (flux decreases) → current induced ✅

so answer C

The figure shows a circular loop of wire falling toward a wire carrying a current to the left. What is the direction of the induced current in the loop of wire?

counterclockwise

According to right hand rule if the magnetic field is directed out of the page the current will induced in the counterclockwise direction. So this option is correct

Faraday’s Law of Induction states that the magnitude of the induced electromotive force (EMF) in a circuit is directly proportional to which of the following?

The rate of change of the magnetic flux

A circular loop of wire is held fixed with its plane parallel to a uniform, time-varying magnetic field. If the magnetic field strength is doubled, what happens to the magnetic flux  Phase b through the loop?

Remains zero

A bar magnet is pushed rapidly into a coil of wire, inducing a current. According to Lenz's Law, the induced current creates a magnetic field that acts to:

repel the magnet opposing its entry into the coil

A square loop of wire with side length  is in a uniform magnetic field . The loop is pulled into a diamond shape (same perimeter) in a time . By what factor does the magnitude of the average induced EMF change if the side length  is doubled, assuming  and remain constant?

it quadruples

A metal rod, 0.50 m long, moves at a constant speed of 2.0 m/s perpendicular to a uniform magnetic field of strength 0.40 T. What is the magnitude of the motional EMF induced across the ends of the rod?

e=Blv=>(0.40)*(0.5m)(2.0)=4.0

A loop of wire is placed in a region of uniform magnetic field, which is directed into the page. If the magnitude of the magnetic field is decreasing, what is the direction of the induced current in the loop, according to Lenz's Law?

clockwise

A circular loop of wire is held in a uniform magnetic field, with the plane of the loop perpendicular to the field lines. Which of the following will not cause a current to be induced in the loop?

1. keeping the orientation of the loop fixed and moving it along the field lines

Consider the circuit in the figure with S, open and S2 at position a.

Switch S, is now thrown closed. At the instant it is closed, across which circuit element is the voltage equal to the emf of the battery?

Inductor

Consider the circuit in the figure with S1 open and S2 at position a.

Switch S1 is thrown closed. After a very long time, across which circuit element is the voltage equal to the emf of the battery?

Resistor