Question 1

Two parallel wires, 4 cm apart, carry currents of 2 A and 4 A respectively, in the same direction.The force per unit length of one wire on the other is: A)1* 10^-3 N/m, repulsive B)1 *10^-3 N/m, attractive C)4* 10^-5 N/m, repulsive D)4 * 10^-5 N/m, attractive E)none of these

Accepted Answer

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Question 2

A long straight wire carrying a 3.0 A current enters a room through a window 1.5 m high and 1.0 m wide.The path integral around the window frame has the value: A)0.20 T.m B)2.5 *10^-7 T.m C)3.0 *10^-7 T.m D)3.8 *10^-6 T.m E)none of these

Accepted Answer

The answer of A long straight wire carrying a 3.0...

Question 3

Two parallel wires carrying equal currents of 10 A attract each other with a force of 1 mN.If both currents are doubled, the force of attraction will be:
A)0.25 mN
B)0.5 mN
C)1 mN
D)2 mN
E)4 mN

Accepted Answer

The answer of Two parallel wires carrying equal currents of...

Question 4

Two long ideal solenoids (with radii 20 mm and 30 mm respectively)have the same number of turns of wire per unit length.The smaller solenoid is mounted inside the larger, along a common axis.It is observed that there is zero magnetic field within the inner solenoid.The current in the inner solenoid must be:
A)two-thirds the current in the outer solenoid
B)one-third the current in the outer solenoid
C)twice the current in the outer solenoid
D)half the current in the outer solenoid
E)the same as the current in the outer solenoid

Accepted Answer

The answer of Two long ideal solenoids (with radii 20...

Question 5

Magnetic field lines inside the solenoid shown are: 
A)clockwise circles as one looks down the axis from the top of the page
B)counterclockwise circles as one looks down the axis from the top of the page
C)toward the top of the page
D)toward the bottom of the page
E)in no direction since B = 0

Accepted Answer

The answer of Magnetic field lines inside the solenoid shown...

Question 6

If the magnetic field is uniform over the area bounded by a circle with a radius R, the net current through the circle is: A)"0" B)"2$\pi$RB$\mu$₀" C)"$\pi$R²B/$\mu$₀" D)"RB/2$\mu$₀" E)"2RB/$\mu$₀"

Accepted Answer

The net current through the circle is zero because the magnetic field is uniform over the area bounded by the circle.

Question 7

In the figure, there are three wires carrying currents in the indicated directions, and an Amperian loop.The sign of the contribution of the current in each wire to the path integral in Ampere's Law is: A)i₁ +, i₂ -, i₃ 0 B)i₁ -, i₂ +, i₃ 0 C)i₁ +, i₂ +, i₃ - D)i₁ -, i₂ -, i₃ + E)i₁ +, i₂ -, i₃ -

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The answer of In the figure, there are three wires...

Question 8

A long straight cylindrical shell carries current i uniformly distributed over its cross section.The magnitude of the magnetic field is greatest:
A)at the inner surface of the shell
B)at the outer surface of the shell
C)inside the shell near the middle
D)in hollow region near the inner surface
E)near the center of the hollow region

Accepted Answer

The magnitude of the magnetic field at any radius r from the axis of the cylindrical shell is given by the formula B = μ0 * i * r / (2 * R^2), where R is the radius of the shell. Since the numerator i * r is maximized at the outer surface of the shell (r = R), and the denominator R^2 is the same for all radii, the magnitude of the magnetic field is greatest at the outer surface of the shell.

Question 9

A long straight cylindrical shell has an inner radius R_i and an outer radius R_o.It carries a current i, uniformly distributed over its cross section.A wire is parallel to the cylinder axis, in the hollow region (r < R_i).The magnetic field is zero everywhere outside the shell (r > R_o).We conclude that the wire: A)is on the cylinder axis and carries current i in the same direction as the current in the shell B)may be anywhere in the hollow region but must be carrying current i in the direction opposite to that of the current in the shell C)may be anywhere in the hollow region but must be carrying current i in the same direction as the current in the shell D)is on the cylinder axis and carries current i in the direction opposite to that of the current in the shell E)does not carry any current

Accepted Answer

By Ampere's Law, the magnetic field inside the hollow region is proportional to the current enclosed by the Amperian loop. Since the wire is outside the current-carrying region (the shell), it does not contribute to the current enclosed by the Amperian loop. Therefore, the magnetic field inside the hollow region must be zero. This means that the wire on the cylinder axis (where the magnetic field is zero) must carry a current in the opposite direction to cancel out the magnetic field due to the current in the shell. Therefore, the correct choice is D.

Question 10

In Ampere's law, , the integration must be over any:
A)surface
B)closed surface
C)path
D)closed path
E)closed path that surrounds all the current producing

Accepted Answer

Ampere's law involves the integration of the magnetic field along a closed path, which is related to the current enclosed by that path.

Question 11

In Ampere's law, the symbol is:
A)an infinitesimal piece of the wire that carries current i
B)in the direction of
C)perpendicular to
D)a vector whose magnitude is the length of the wire that carries current i
E)none of the above

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The answer of In Ampere's law, the symbol is:
A)an infinitesimal...

Question 12

In Ampere's law, the direction of the integration around the path:
A)must be clockwise
B)must be counterclockwise
C)must be such as to follow the magnetic field lines
D)must be along the wire in the direction of the current
E)none of the above

Accepted Answer

Ampere's law does not specify a direction for the integration path; it can be chosen arbitrarily as long as it forms a closed loop. The direction is typically chosen based on convenience or symmetry.

Question 13

A constant current is sent through a helical coil made of flexible wire.The coil:
A)tends to get shorter
B)tends to get longer
C)tends to rotate about its axis
D)produces zero magnetic field at its center
E)none of the above

Accepted Answer

When a constant current is sent through a helical coil, the coil tends to get shorter due to the magnetic field created by the current. This field exerts a force on different parts of the coil, pulling the turns of the coil closer together.

Question 14

The magnetic field at any point in the xy plane is given by , where is the position vector of the point, A is a constant, and is a unit vector in the +z direction.The net current through a circle of radius R, in the xy plane and centered at the origin is given by: A)" $\pi$AR²/$\mu$₀" B)"2 $\pi$AR/$\mu$₀" C)"4 $\pi$AR³/3$\mu$₀" D)"2 $\pi$AR²/$\mu$₀" E)" $\pi$AR²/2$\mu$₀"

Accepted Answer

The answer of The magnetic field at any point in...

Question 15

The magnetic field inside a long ideal solenoid is independent of:
A)the current
B)the number of turns of wire
C)the spacing of the windings
D)the cross-sectional area
E)the direction of the current

Accepted Answer

The magnetic field inside a long ideal solenoid is determined by the current and the number of turns per unit length, and is independent of the cross-sectional area.

Question 16

Two parallel wires, 4 cm apart, carry currents of 2 A and 4 A respectively, in opposite directions.The force per unit length of one wire on the other is: A)1 * 10^-3 N/m, repulsive B)1 * 10^-3 N/m, attractive C)4 *0 10^-5 N/m, repulsive D)4 * 10^-5 N/m, attractive E)none of these

Accepted Answer

The force per unit length between the two wires is given by the equation $F = \frac{\mu_0 I_1 I_2}{2\pi d}$, where $\mu_0$ is the permeability of free space, $I_1$ and $I_2$ are the currents in the wires, and $d$ is the distance between the wires. Substituting the given values, we get:

$F = \frac{(4\pi 	imes 10^{-7}	ext{ T}\cdot	ext{m}/	ext{A})(2	ext{ A})(4	ext{ A})}{2\pi(0.04	ext{ m})} = 4	imes 10^{-5}$ N/m

Since the currents are flowing in opposite directions, the force will be repulsive, pushing the wires away from each other. Therefore, the best choice is (C).

Question 17

Two long straight wires enter a room through a window.One carries a current of 3.0 A into the room while the other carries a current of 5.0 A out.The magnitude of the path integral around the window frame is: A)2.5 * 10^-6T.m B)3.8 *10^-6 T.m C)6.3 * 10^-6T.m D)1.0* 10^-5.m E)none of these

Accepted Answer

The answer of Two long straight wires enter a room...

Question 18

Two parallel long wires carry the same current and repel each other with a force F per unit length.If both these currents are doubled and the wire separation tripled, the force per unit length becomes:
A)2F/9
B)4F/9
C)2F/3
D)4F/3
E)6F

Accepted Answer

The answer of Two parallel long wires carry the same...

Question 19

A long straight cylindrical shell has an inner radius R_i and an outer radius R_o.It carries a current i, uniformly distributed over its cross section.A wire is parallel to the cylinder axis, in the hollow region (r < R_i).The magnetic field is zero everywhere in the hollow region.We conclude that the wire: A)is on the cylinder axis and carries current i in the same direction as the current in the shell B)may be anywhere in the hollow region but must be carrying current i in the direction opposite to that of the current in the shell C)may be anywhere in the hollow region but must be carrying current i in the same direction as the current in the shell D)is on the cylinder axis and carries current i in the direction opposite to that of the current in the shell E)does not carry any current

Accepted Answer

The answer of A long straight cylindrical shell has an...

Question 20

Four long straight wires carry equal currents into the page as shown.The magnetic force exerted on wire F is: 
A)north
B)east
C)south
D)west
E)zero

Accepted Answer

The answer of Four long straight wires carry equal currents...

Quiz 29: Magnetic Fields Due to Currents

Two parallel wires, 4 cm apart, carry currents of 2 A and 4 A respectively, in the same direction.The force per unit length of one wire on the other is:

A long straight wire carrying a 3.0 A current enters a room through a window 1.5 m high and 1.0 m wide.The path integral around the window frame has the value:

Two parallel wires carrying equal currents of 10 A attract each other with a force of 1 mN.If both currents are doubled, the force of attraction will be:

Magnetic field lines inside the solenoid shown are:

If the magnetic field is uniform over the area bounded by a circle with a radius R, the net current through the circle is:

In the figure, there are three wires carrying currents in the indicated directions, and an Amperian loop.The sign of the contribution of the current in each wire to the path integral in Ampere's Law is:

A long straight cylindrical shell carries current i uniformly distributed over its cross section.The magnitude of the magnetic field is greatest:

In Ampere's law, , the integration must be over any:

In Ampere's law, the symbol is:

In Ampere's law, the direction of the integration around the path:

A constant current is sent through a helical coil made of flexible wire.The coil:

The magnetic field at any point in the xy plane is given by , where is the position vector of the point, A is a constant, and is a unit vector in the +z direction.The net current through a circle of radius R, in the xy plane and centered at the origin is given by:

The magnetic field inside a long ideal solenoid is independent of:

Two parallel wires, 4 cm apart, carry currents of 2 A and 4 A respectively, in opposite directions.The force per unit length of one wire on the other is:

Two long straight wires enter a room through a window.One carries a current of 3.0 A into the room while the other carries a current of 5.0 A out.The magnitude of the path integral around the window frame is:

Two parallel long wires carry the same current and repel each other with a force F per unit length.If both these currents are doubled and the wire separation tripled, the force per unit length becomes:

Four long straight wires carry equal currents into the page as shown.The magnetic force exerted on wire F is: