# Worksheet: Propagating Electric and Magnetic Fields

In this worksheet, we will practice modeling electromagnetic waves as propagating electric and magnetic fields.

Q1:

Electromagnetic waves propagate through water that has a refractive index of 1.33. The electric permittivity of the water is C2/N⋅m2. What is the magnetic permeability of the water?

• A H/m
• B H/m
• C H/m
• D H/m
• E H/m

Q2:

Which of the following formulas correctly shows the relation between , the speed at which electromagnetic waves propagate through a medium; , the electric permittivity of the medium; and , the magnetic permeability of the medium?

• A
• B
• C
• D
• E

Q3:

At what speed do electromagnetic waves propagate in a vacuum? Answer to two significant figures.

• A m/s
• B m/s
• C m/s
• D m/s
• E m/s

Q4:

Which of the following statements about the energy transferred by the electric and magnetic fields that electromagnetic waves are comprised of is correct?

• AThe energy transferred by the electric field of an electromagnetic wave is greater than the energy transferred by the magnetic field of the electromagnetic wave.
• BThe energy transferred by the electric field of an electromagnetic wave is equal to the energy transferred by the magnetic field of the electromagnetic wave.
• CThe energy transferred by an electromagnetic wave is equal to the difference between the energy transferred by the wave’s electric and magnetic fields.
• DThe energy transferred by the magnetic field of an electromagnetic wave is greater than the energy transferred by the electric field of the electromagnetic wave.

Q5:

Electromagnetic waves propagate through rubber that has a refractive index of 1.5. The electric permittivity of the rubber is C2/N⋅m2. What is the magnetic permeability of the rubber?

• A H/m
• B H/m
• C H/m
• D H/m
• E H/m

Q6:

Which of the following diagrams correctly shows how the electric field , shown in yellow, and the magnetic field , shown in green, that an electromagnetic wave is comprised of vary with time ?

• A • B • C • D Q7:

A material has an electric permittivity of C2/N⋅m2 and a magnetic permeability of H/m. What is the refractive index of the material?

Q8:

The diagram shows a conducting wire and the magnetic field around it at an instant . At the instant , the magnetic field around the wire has a nonzero magnitude only as far from the wire as the point that intersects the line . The current in the wire is initially zero at an instant , which occurs well before . The current increases from a value of zero at the instant to a constant nonzero value. The time taken for the current to reach its constant nonzero value is much less than . Between which of the points that intersect the lines , , and does the magnetic field strength around the wire not change with time just after the instant ?

• A and
• B and
• CNone of these points
• D and

Between which of the points that intersect the lines , , and is the magnetic field strength constant with the distance from the wire at the instant ?

• A and
• BNone of these points
• C and
• D and

Between which of the points that intersect the lines , , and does the magnetic field strength change with time just after the instant ?

• A and
• B and
• C and
• DNone of these points

Between which of the points that intersect the lines , , and is an electric field present at the instant ?

• ANone of these points
• B and
• C and
• D and

Between which of the points that intersect the lines , , and is an electric field that is changing strength present just after the instant ?

• ANone of these points
• B and
• C and
• D and