Question

If someone can answer any/all of these that would be much appreciated!

C. 7. Which of the following best describes the Junction Rule, one of Kirchoff's Rules? a. Current can only run out of a junction b. Current can only run into a junction Current can't flow through a junction d. The total amount of current flowing into a junction equals the total amount of current running out of a junction 8. A positively charged particle moves in the + x direction. The magnetic field in the region points in the - x direction. What is the direction of the magnetic force on the moving charge? a. The +x direction b. The -x direction c. Some other direction d. No direction (Ě = 0) 9. Which of the following causes an induced current in a loop of wire? a. Having an electric flux in the loop b. Changing the electric flux in the loop C. Having a magnetic flux in the loop d. Changing the magnetic flux in the loop 10. What causes a divergence in the magnetic field (i.e. the magnetic field pointing outward from a point)? a. Electric current b. Electric charge c. A changing electric field d. A changing magnetic field e. Nothing. It doesn't happen. Name: 11. Which best describes the direction an electromagnetic wave propagates (i.e. wave velocity direction)? a. Along the electric field b. Along the magnetic field c. Perpendicular to both the electric and magnetic field. 12. If a speaker increases the frequency it produces while the conditions in the air remain the same, what happens? a. The wave speed increases b. The wave speed decreases c. The wavelength increases d. The wavelength decreases

Answer 1

Solution:

Q: 7

Answer: d

Explanation: At a junction, there will be both currents entering into and currents leaving the junction.

Kirchhoff's Junction Laws states that " the total amount of current flowing into the junction equals the total amount of current leaving the junction."

Q: 8

Answer: d (no direction)

Explanation: The force on a charged particle moving in a magnetic field is given by F = qvBsin$\theta$ ;

where  $\theta$ is the angle between the direction of velocity(v) of the charged particle and the direction of magnetic field(B).

Here, the charged particle is moving antiparallel to the direction of magnetic field. So, the angle $\theta$ = 180^o.

As sin180^o = 0, F = 0.

Hence, the charged particle does not experience any force in any direction.

Q: 9

Answer: d

Explanation: Only a changing magnetic flux linked with a coil, produces an induced current in the loop.

The flux linked with the coil can be changed with a varying magnetic field or due to the relative motion between the magnetic field and the coil.

Q: 10

Answer: e

Explanation: Since magnetic monopoles do not exist, the field cannot diverge from a point or converge to a point.

As we know, the magnetic field lines are continuous, closed loops. That means there is no starting or ending point of field line.

If we imagine a closed surface enclosing a bar magnet, the magnetic number of field lines entering the surface is equal to the number of field lines leaving it. So, there will be no net outflow or inflow of the field.

So, divergence of magnetic field does not happen.

Q: 11

Answer: c

Explanation: Electromagnetic wave is transverse in nature. Electric field, magnetic field, and the direction of propagation of wave, all three are mutually perpendicular. That means both electric and magnetic fields are perpendicular to each other, and the wave propagates in a direction perpendicular to both electric and magnetic fields.

For example, if electric field is along X direction and magnetic field is along Y direction, then the wave propagates(direction of velocity of wave) in the Z direction.

Q: 12

Answer: d

If the speaker increases the frequency, the wavelength decreases.

Explanation: The relation between wavelength($\lambda$), frequency($\nu$), and speed(v) of sound wave(or any wave), is

v = $\nu$ $\lambda$

As the conditions in the air remain the same, the speed of sound wave remains constant.

Hence, to keep the wave speed constant, with the increase in frequency, the wavelength of the wave is decreased.