Q: If the direction of the electric field $$\vec{E}$$ and magnetic field $$\vec{B} of an $$electromagnetic wave are given, what is the direction of propagation of the wave?

In the direction of $$\vec{E} \times \vec{B}$$

Question 1

A very long straight wire carries a uniform linear charge density $$\lambda. $$What is the expression for the electric field $$E at a $$distance $$r$$ from the wire?

Accepted Answer

$$E = \dfrac{\lambda}{2\pi\$$epsilon_0$$ r}$$

Question 2

If the electric field $$E$$ between two parallel plates is halved, what happens to the surface charge density $$\sigma on $$the plates?

Accepted Answer

$$\sigma is $$halved

Question 3

A wire of length $$L$$ and resistivity $$\rho$$ has a resistance $$R. If $$the diameter of the wire is doubled, what happens to the resistance?

Accepted Answer

Resistance becomes one-fourth of the original value

Question 4

Three resistors $$R_1$$, $$R_2$$, and $$R_3$$ are connected in series. What is the total resistance $$R_s$$?

Accepted Answer

$$R_s = R_1$ + R_2$ + R_3$

Question 5

A parallel plate capacitor is connected to a battery. If a dielectric is inserted between the plates, what happens to the voltage $$V$$ and the electric field $$E$$ across the plates?

Accepted Answer

Voltage remains the same, electric field decreases

Question 6

Two long parallel wires carry equal currents in opposite directions. Where is the magnetic field between the wires zero?

Accepted Answer

At a point between the wires, equidistant from both

Question 7

A solenoid has a radius $$r$$ and carries a current $$I. If $$the magnetic field $$B$$ and the electric field $$E at a $$distance from the axis are known, how can you find the radius of the solenoid?

Accepted Answer

By using the relationship between $$E$$, $$B$$, and $$r$$ specific to the solenoid's geometry

Question 8

The energy density $$u in a $$magnetic field is given by which formula?

Accepted Answer

$$u = \dfrac{B^2$}{2\mu_0$}$$

Question 9

A long straight wire carries a current $$I. $$What is the magnetic field $$B at a $$distance $$r$$ from the wire?

Accepted Answer

$$B = \dfrac{\mu_0$ I}{2\pi r}$$

Question 10

According to Faraday's law, what is the induced emf $$\epsilon in a $$coil with inductance $$L$$ when the current changes at a rate $$\dfrac{di}{dt}$$?

Accepted Answer

$$\epsilon = -L \dfrac{di}{dt}$$

Question 11

Which statement about electromagnetic waves is correct?

Accepted Answer

They are transverse waves and do not require a medium to propagate

Question 12

In the electromagnetic spectrum, which type of wave has the highest frequency?

Accepted Answer

Gamma rays

Question 13

If the direction of the electric field $$\vec{E}$$ and magnetic field $$\vec{B} of an $$electromagnetic wave are given, what is the direction of propagation of the wave?

Accepted Answer

In the direction of $$\vec{E} 	imes \vec{B}$$

Question 14

An electromagnetic wave is propagating in the $$+x$$ direction. If the electric field is $$E = 0.2 \sin(kx - \omega t) V/m$$, what is the magnitude of the Poynting vector $$S$$?

Accepted Answer

$$S = \dfrac{E^2$}{\mu_0$ c}$$

Question 15

If the index of refraction of a material is $$n$$, what is the speed of light $$v in $$that material?

Accepted Answer

$$v = \dfrac{c}{n}$$

Question 16

When a ray passes from air ($$n_1 = 1$) into glass (n_2$ = 1.5$$), which statement is true about the angle of refraction $$\$$theta_2$$ compared to the angle of incidence $$\$$theta_1$$?

Accepted Answer

$$\$$theta_2$$ \u003c \$$theta_1$$

Question 17

Total internal reflection occurs only when light travels from a medium with index $$n_1 to a $$medium with index $$n_2$$ such that:

Accepted Answer

$$n_1$$ \u003e $$n_2$$

Question 18

What is the formula for the critical angle $$	heta_c$$ for total internal reflection when light passes from medium 1 ($$n_1) to $$medium 2 ($$n_2$$)?

Accepted Answer

$$\sin 	heta_c = \dfrac{n_2$}{n_1$}$$

Question 19

A wire of length $$L$$ and area $$A$$ has resistance $$R. If $$the resistivity is $$\rho$$, what is the correct formula for $$R$$?

Accepted Answer

$$R = \dfrac{\rho L}{A}$$

Comprehensive Physics Review: Electricity, Magnetism, and Electromagnetic Waves

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