Physics 2 Final Exam Ch. 27,28

Two bar magnets with S end and a S end, the magnetic field is

0

A rectangular coil, with corners labeled ABCD, of length L and width w is placed in a magnetic field B as shown in Fig. 27-5. If there is no current flowing through the coil, what is the force acting on section AB of the coil?

0 N

Three particles travel through a region of space where the magnetic field is out of the page, as shown in Fig. 27-4. The electric charge of each of the three particles is, respectively,

1 is negative, 2 is neutral, 3 is positive

The figure below shows 2 bar magnets of the same size and the same strength. Which of the arrows labeled A to D correctly represents the direction of the magnetic field at a point located at the common origin of the arrows? (That point is at an equal distance from the two magnets.)

A (pointing straight up)

A wire of length L carrying a current I is placed in a magnetic field. The direction of the magnetic field is opposite the direction of the current. In this situation, the wire experiences a maximum force. T or F

False

Ampère's law can be used to analytically find the magnetic field at the center of a circle formed by a current-carrying conductor. T or F

False

Ampère's law can be used to analytically find the magnetic field at the center of a square loop carrying a constant current. T or F

False

Cutting a bar magnet near its north end results in a smaller mostly north pole magnet and a larger mostly south pole magnet. T or F

False

If two identical wires carrying a certain current in the same direction are placed parallel to each other, they will experience a force of repulsion. T or F

False

The magnetic field near a current carrying wire is directly proportional to the distance from the wire. T or F

False

The magnitude of the magnetic field inside a solenoid is inversely proportional to the current flowing through the solenoid. T or F

False

A vertical wire carries a current straight down. To the east of this wire, the magnetic field points

South

A charged particle traveling opposite to a magnetic field does not experience a magnetic force. T or F

True

A current carrying wire placed in a magnetic field perpendicular to the wire experiences a maximum force. T or F

True

A rectangular coil carrying a current in a magnetic field will experience a net torque that will cause the coil to rotate in that field, if the field is not along the coil axis. T or F

True

Ampère's law can be used to analytically find the magnetic field inside a toroid. (A toroid is a doughnut shape wound uniformly with many turns of wire.) T or F

True

At a given location the direction of the magnetic field is the direction that the north pole of a compass points when placed at that location. T or F

True

In a velocity selector having electric field E and magnetic field B, the velocity selected for positively charged particles is v = E/B. The formula is the same for a negatively charged particles. T or F

True

Magnetic field lines can never cross one another. T or F

True

The field outside a solenoid behaves like that of a bar magnet. T or F

True

The magnetic field unlike the electric field is continuous. T or F

True

Which of the following is correct?

When a current carrying wire is in your right hand, thumb in the direction of the current, your fingers point in the direction of the magnetic field lines.

Which of the following choices of path allow you to use Ampère's law to analytically find B⃗ (r⃗ )? (a) The path must pass through the point r⃗ . (b) The path must have enough symmetry so that B⃗ (r⃗ )⋅dl⃗ is constant along large parts of it. (c.)The path must be a circle.

a and b

What fundamental fact underlies the operation of essentially all electric motors?

a current-carrying conductor is placed perpendicular to a magnetic field will experience a force

An electric current produces

a magnetic field

The circle on the integral means that B⃗ (r⃗ ) must be integrated (∮B⃗ (r⃗ )⋅dl⃗ =μ0Iencl.)

along any closed path that you choose

A piece of soft iron is placed in a solenoid increasing the magnetic field in an arrangement that can be switched on and off. Such a device is called

an electromagnet

In using Ampere's law, the integral must be evaluated

around a closed path

A horizontal wire carries a current straight toward you. From your point of view, the magnetic field caused by this current

circles the wire in a counter clockwise direction

A long, straight wire carrying a current is placed along the y-axis. If the direction of the current is in the +y direction, what is the direction of the magnetic field due to this wire?

counterclockwise around the y-axis

A charged particle is injected into a uniform magnetic field such that its velocity vector is perpendicular to the magnetic field vector. Ignoring the particle's weight, the particle will

follow a circular path

A square loop of wire carrying a current in a clockwise direction lies in the plane of the paper. The magnetic field inside the loop is directed

into the paper everywhere

Two long parallel wires placed side-by-side on a horizontal table carry identical current straight toward you. From your point of view, the magnetic field at the point exactly between the two wires

is zero

You are looking straight down on a magnetic compass that is lying flat on a table. A wire is stretched horizontally under the table, parallel to and a short distance below the compass needle. The wire is then connected to a battery so that a current I flows through the wire. This current causes the north pole of the compass needle to deflect to the left. The questions that follow ask you to compare the effects of different actions on this initial deflection.With the wire back at its initial location, you connect a second identical battery in series with the first one. When you close the switch, how does the new angle of deflection of the north pole of the compass needle compare to its initial deflection?

it is larger

You are looking straight down on a magnetic compass that is lying flat on a table. A wire is stretched horizontally under the table, parallel to and a short distance below the compass needle. The wire is then connected to a battery so that a current I flows through the wire. This current causes the north pole of the compass needle to deflect to the left. The questions that follow ask you to compare the effects of different actions on this initial deflection.If the wire is lowered farther from the compass, how does the new angle of deflection of the north pole of the compass needle compare to its initial deflection?

it is smaller

The magnetic permeability of a ferromagnetic material is

much greater than mu knot

A rectangular coil, with corners labeled ABCD, of length L and width w is placed in a magnetic field B as shown in Figure 27-6. If there is a current I flowing through this coil, what is the direction of the force acting on section AB of this coil?

perpendicular and into the page

A rectangular coil, with corners labeled ABCD, of length L and width w is placed in a magnetic field B as shown in Figure 27-6. If there is a current I flowing through this coil, what is the direction of the force acting on section CD of this coil?

perpendicular to and out of the page

The direction of the force on a current-carrying wire in a magnetic field is described by which of the following?

perpendicular to both the current and the magnetic field

Two long parallel wires placed side-by-side on a horizontal table carry identical size currents in opposite directions. The wire on your right carries current toward you, and the wire on your left carries current away from you. From your point of view, the magnetic field at the point exactly midway between the two wires

points down

A current carrying loop of wire lies flat on a table top. When viewed from above, the current moves around the loop in a counterclockwise sense. What is the direction of the magnetic field caused by this current, outside the loop? The magnetic field

points straight down

A current carrying circular loop of wire lies flat on a table top. When viewed from above, the current moves around the loop in a counterclockwise sense. What is the direction of the magnetic field caused by this current, inside the loop? The magnetic field

points straight up

The magnetic field produced by a long straight current-carrying wire is

proportional to the current in the wire and inversely proportional to the distance from the wire.

The force on a current-carrying wire in a magnetic field is equal to zero when

the current is parallel to the field lines

The integral on the left is: (Ampère's law is often written ∮B⃗ (r⃗ )⋅dl⃗ =μ0Iencl)

the line integral along the closed loop

(Ampère's law is often written ∮B⃗ (r⃗ )⋅dl⃗ =μ0Iencl) What physical property does the symbol Iencl represent?

the net current through the loop

Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry current in opposite directions,

the wires repel each other

A proton, moving west, enters a magnetic field of a certain strength. Because of this magnetic field the proton curves upward. What is the direction of this magnetic field?

towards the south

An electron, moving south, enters a magnetic field of certain strength. Because of this field the electron curves upward. What is the direction of the magnetic field?

towards the west

Ampère's law can be used to analytically find the magnetic field around a straight current-carrying wire. T or F

true

The ampere is defined

using the force between the current carrying wires

A vertical wire carries a current straight up in a region where the magnetic field vector points due north. What is the direction of the resulting force on this current?

west