Question 1

A circular coil with 130 turns and an area of $$9.0 	imes 10$$^{-3}$$ \ \mathrm{m}^2 is $$placed in a uniform magnetic field of $$1.6 \ \mathrm{T}$$, which makes an angle of $$35^\circ$$ with the plane of the coil. What is the correct formula to calculate the magnetic flux through the coil?

Accepted Answer

$$\Phi = N A B \cos (90^\circ - \phi)$$

Question 2

Given a coil with $$N = 130$$ turns, $$A = 9.0 	imes 10$$^{-3}$$ \ \mathrm{m}^2$$, $$B = 1.6 \ \mathrm{T}$$, and the field at $$35^\circ to $$the plane of the coil, what is the magnetic flux through the coil? (Use $$\Phi = N A B \cos(90^\circ - 35^\circ)$$ and round to 2 significant figures.)

Accepted Answer

$$1.1$$

Question 3

A conducting coil lies flat on a level tabletop in a region where the magnetic field points straight up. The magnetic field suddenly grows weaker. When viewed from above, what is the direction of the induced current in this coil as the field decreases?

Accepted Answer

counterclockwise

Question 4

A single-turn loop of wire with resistance $$6.00\ \Omega$$ and area $$300.0\ \mathrm{cm}^2 is $$perpendicular to a uniform magnetic field that increases from $$0.200\ \mathrm{T} to$$ $$3.60\ \mathrm{T} in$$ $$0.500\ \mathrm{s}. $$What is the magnitude of the induced current in the loop (in mA)?

Accepted Answer

$$34.0$$

Question 5

Which equation correctly expresses Faraday's Law for the magnitude of the induced emf in a loop when the magnetic field changes?

Accepted Answer

$$\mathcal{E} = |\Delta \Phi / \Delta t|$$

Question 6

An electromagnetic wave is propagating in the $$+z$$ direction. At a particular moment, you measure the electric field to be in the $$-y$$ direction. What is the direction of the magnetic field at that moment?

Accepted Answer

$$+x$$ direction

Question 7

In the vacuum of space, which statement correctly compares the energies and speeds of an infrared photon to a visible photon?

Accepted Answer

The visible photon is more energetic, and they have the same speed.

Question 8

A loop of wire is placed in a region where the magnetic field is perpendicular to the plane of the loop and is increasing. According to Lenz's Law, what is the direction of the induced current?

Accepted Answer

The current will flow to produce a magnetic field opposing the increase.

Question 9

A magnet is moving upward through a loop, causing the downward magnetic flux to decrease. What is the direction of the induced current in the loop as seen from above?

Accepted Answer

clockwise

Question 10

Which of the following best describes the relationship between the frequency and energy of a photon?

Accepted Answer

$$E = h f$$

Question 11

A coil is oriented so that the angle between the magnetic field $$\vec{B}$$ and the normal to the coil is $$	heta. $$Which formula gives the magnetic flux through the coil?

Accepted Answer

$$\Phi = N A B \cos 	heta$$

Question 12

If the area of a coil is doubled while keeping the magnetic field and the angle constant, what happens to the magnetic flux through the coil?

Accepted Answer

It doubles.

Question 13

A loop of wire is placed in a region where the magnetic field is perpendicular to the plane of the loop and is decreasing. What is the direction of the induced current as seen from above?

Accepted Answer

counterclockwise

Question 14

Which of the following is true about the speed of electromagnetic waves in a vacuum?

Accepted Answer

All electromagnetic waves travel at the same speed, $$c = 3.00 	imes 10^8$ \ \mathrm{m/s}.$$

Question 15

A wire loop of area $$A$$ and resistance $$R is $$placed in a magnetic field that changes from $$B_i to$$ $$B_f in $$time $$\Delta t. $$What is the formula for the induced current?

Accepted Answer

$$I = \frac{A (B_f - B_i)}{R \Delta t}$$

Question 16

Which of the following statements about electromagnetic waves is correct?

Accepted Answer

The electric and magnetic fields are perpendicular to each other and to the direction of propagation.

Magnetic Flux, Induced Current, and Electromagnetic Waves – Step-by-Step Physics Guidance

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