AP Physics 2: Algebra-Based Practice Quiz: Magnetism and Current-Carrying Wires

Correct Answer: B

Content point 3 explicitly states: 'A current-carrying wire produces a magnetic field.'

Correct Answer: B

Content point 4 states that the magnetic field B is proportional to the current I ($B=rac{\mu_0}{2\pi}rac{I}{r}$). Therefore, if the current I is doubled, the magnetic field B must also double.

Correct Answer: C

Content point 4 states that the magnitude of the magnetic field is 'inversely proportional to the perpendicular distance from the central axis of the wire to the point.' This relationship is shown in the equation $B=rac{\mu_0}{2\pi}rac{I}{r}$.

Correct Answer: B

Content point 5 clearly states: 'The direction of the magnetic field created by a current-carrying wire is determined with the right-hand rule.'

Correct Answer: C

According to content point 6, the magnitude of the magnetic force is given by $F_B = I\ell B\sin heta$. The force is directly proportional to the length ℓ of the wire within the field. Therefore, if ℓ is doubled, the force $F_B$ is also doubled.

Correct Answer: C

The force equation is $F_B = I\ell B\sin heta$. The sine function, $\sin heta$, has a maximum value of 1 when the angle θ is 90°. Therefore, the force is maximized when the current is perpendicular to the magnetic field.

Correct Answer: B

The force equation is $F_B = I\ell B\sin heta$. The force is zero when $\sin heta = 0$. This occurs when the angle θ is 0° or 180°, which means the current is parallel or anti-parallel to the magnetic field direction.

Correct Answer: A

The magnetic field is given by $B=rac{\mu_0}{2\pi}rac{I}{r}$. The new current is I/2 and the new distance is 2r. The new field B' will be proportional to (I/2)/(2r) = I/(4r). Therefore, the new field is one-fourth of the original field, or B/4.

Correct Answer: D

Content point 6 states that the force is proportional to the current (I), the length of the wire (ℓ), and the magnitude of the magnetic field (B), as shown in the equation $F_B = I\ell B\sin heta$. The resistance of the wire is not a direct factor in this equation.

Correct Answer: C

Content point 2 directly states: 'Describe the force exerted on a current-carrying wire by a magnetic field.' This indicates a force is the fundamental interaction.

Correct Answer: B

Content point 6 specifies that the force 'depends on the angle between the direction of the current in the wire and the direction of the magnetic field.' This is the angle θ in the equation.

Correct Answer: C

The original force is $F = I\ell B\sin(90^\circ) = I\ell B$. The new force F' is calculated with the new length (ℓ/3) and new field (3B): $F' = I(\ell/3)(3B)\sin(90^\circ) = I\ell B$. The new force is the same as the original force F.

Correct Answer: C

Content point 4 states that the magnitude of the magnetic field is 'inversely proportional to the perpendicular distance from the central axis of the wire.' This means as the distance (r) increases, the field strength (B) decreases.

Correct Answer: C

Based on content point 4, the equation relates the magnetic field (B) to the current (I) and distance (r). The text states that B is 'proportional to the magnitude of the current in the wire,' identifying 'I' as the current.

Correct Answer: C

The force on Wire 2 depends on its own current, its length, and the magnetic field it is in ($F_2 = I_2\ell B_1\sin heta$). The magnetic field it is in, B1, is produced by Wire 1 and is proportional to the current in Wire 1 ($B_1 \propto I_1$). Therefore, the force on Wire 2 is proportional to the current in Wire 1 ($F_2 \propto B_1 \propto I_1$). If the current in Wire 1 is tripled, the magnetic field it produces is tripled, and consequently, the force on Wire 2 is tripled.