Physics final practice quizes 29,30,32

In an electromagnetic wave, the electric and magnetic fields are oriented such that they are

perpendicular to one another and perpendicular to the direction of wave propagation.

A circular coil of radius 5.0 cm and resistance 0.20Ω0.20⁢Ω is placed in a uniform magnetic field perpendicular to the plane of the coil. The magnitude of the field changes with time according to B=0.50e−20tTB=0.50e−20t⁢T. What is the magnitude of the current induced in the coil at the time t=2.0st=2.0⁢s?

2.6 mA

If an electromagnetic wave has components Ey=E0sin(kx−ωt)Ey=E0⁢sin⁡(k⁢x−ω⁢t) and Bz=B0sin(kx−ωt)Bz=B0⁢sin⁡(k⁢x−ω⁢t), in what direction is it traveling?

+x

At a certain instant the current flowing through a 5.0-H inductor is 3.0 A. If the energy in the inductor at this instant is increasing at a rate of 3.0 J/s, how fast is the current changing?

0.20 A/s

A conducting bar slides without friction on two parallel horizontal rails that are 50 cm apart and connected by a wire at one end. The resistance of the bar and the rails is constant and equal to 0.10Ω0.10⁢Ω. A uniform magnetic field is perpendicular to the plane of the rails. A 0.080-N force parallel to the rails is required to keep the bar moving at a constant speed of 0.50 m/s. What is the magnitude of the magnetic field?

0.25 T

If a beam of electromagnetic radiation has an intensity of 120W/m2120⁢Wm2, what is the maximum value of the electric field? (c=3.0×108m/sc=3.0×108⁢ms, μ0=4π×10−7T⋅m/Aμ0=4⁢π×10−7⁢T⋅m/A, ε0=8.85×10−12C2/N⋅m2ε0=8.85×10−12⁢C2/N⋅m2)

0.30kV/m

A ten-loop coil having an area of 0.23m20.23⁢m2 and a very large resistance is in a 0.047-T uniform magnetic field oriented so that the maximum flux goes through the coil. The coil is then rotated so that the flux through it goes to zero in 0.34 s. What is the magnitude of the average emf induced in the coil during the 0.34 s?

0.32 V

A closed loop conductor that forms a circle with a radius of 2.0 m is located in a uniform but changing magnetic field. If the maximum emf induced in the loop is 5.0 V, what is the maximum rate at which the magnetic field strength is changing if the magnetic field is oriented perpendicular to the plane in which the loop lies?

0.40 T/s

A microwave oven operates with sinusoidal microwaves at a frequency of 2400 MHz. The height of the oven cavity is 25 cm and the base measures 30 cm by 30 cm. Assume that microwave energy is generated uniformly on the upper surface of the cavity and propagates directly downward toward the base. The base is lined with a material that completely absorbs microwave energy. The total microwave energy content of the cavity is 0.50µJ0.50⁢µJ. What is the power output of the oven? (c=3.0×108m/sc=3.0×108⁢ms, μ0=4π×10−7T⋅m/Aμ0=4⁢π×10−7⁢T⋅m/A, ε0=8.85×10−12C2/N⋅m2ε0=8.85×10−12⁢C2/N⋅m2)

0.60 kW

What resistance should be added in series with a 3.0-H inductor to complete an LR circuit with a time constant of 4.0 ms?

0.75kΩ

A loop of radius r=3.0cmr=3.0⁢cm is placed parallel to the xy-plane in a uniform magnetic field →B=0.75Tˆk.B→=0.75⁢Tk^. The resistance of the loop is 18Ω18⁢Ω. Starting at t=0t=0, the magnitude of the field decreases uniformly to zero in 0.15 seconds. What is the magnitude of the electric current produced in the loop during that time?

0.79 mA

A series LR circuit consists of a 2.0-H inductor with negligible internal resistance, a 100-ohm resistor, an open switch, and a 9.0-V ideal power source. After the switch is closed, what is the maximum power delivered by the power supply?

0.81 W

If the intensity of an electromagnetic wave is 80MW/m280⁢MW/m2, what is the amplitude of the magnetic field of this wave? (c=3.0×108m/sc=3.0×108⁢ms, μ0=4π×10−7T⋅m/Aμ0=4⁢π×10−7⁢T⋅m/A, ε0=8.85×10−12C2/N⋅m2ε0=8.85×10−12⁢C2/N⋅m2)

0.82mT

A 2.0-m long conducting wire is formed into a square and placed in the horizontal xy-plane, A uniform magnetic field is oriented 30.0°30.0° above the horizontal with a strength of 9.0 T. What is the magnetic flux through the square?

1.1T⋅m2

An LR circuit contains an ideal 60-V battery, a 51-H inductor having no resistance, a 21-Ω21-Ω resistor, and a switch S, all in series. Initially, the switch is open and has been open for a very long time. At time t=0st=0⁢s, the switch is suddenly closed. When the voltage across the resistor is equal to the voltage across the inductor, what is the current in the circuit?

1.4 A

An LR circuit contains an ideal 60-V battery, a 42-H inductor having no resistance, a 24-Ω24-Ω resistor, and a switch S, all in series. Initially, the switch is open and has been open for a very long time. At time t=0st=0⁢s, the switch is suddenly closed. How long after closing the switch will the potential difference across the inductor be 24 V?

1.6 s

If the electric field and magnetic field of an electromagnetic wave are given by E=E0sin(kx−(t)E=E0⁢sin⁡(k⁢x−(t) and B=B0sin(kx−ωt)B=B0⁢sin⁡(k⁢x−ω⁢t), and if the value of E0E0 is 51µV/m51⁢µV/m, what is the value of B0B0? (c=3.0×108m/s)

1.7×10^−13T

A series LR circuit contains an emf source of 14 V having no internal resistance, a resistor, a 34 H inductor having no appreciable resistance, and a switch. If the emf across the inductor is 80%80% of its maximum value 4.0 s after the switch is closed, what is the resistance of the resistor?

1.9Ω

At what rate would the current in a 100-mH inductor have to change to induce an emf of 1000 V in the inductor?

10,000 A/s

A solenoid of length 0.700 m having a circular cross-section of radius 5.00 cm stores 6.00µJ6.00⁢µJ of energy when a 0.400-A current runs through it. What is the winding density of the solenoid? (μ0=4π×10−7T⋅m/A)

104 turns/m

A 22.0-kg mirror with a surface area of 1.0m21.0⁢m2 and a 98%98% reflectivity is bombarded by light of average intensity 770.0W/m2770.0⁢Wm2 at an angle of 30.0°30.0° to the normal of its surface. If the light has a duration of 0.60 s, how much does the velocity of the mirror change during that time? (c=3.0×108m/sc=3.0×108⁢ms, μ0=4π×10−7T⋅m/Aμ0=4⁢π×10−7⁢T⋅m/A, ε0=8.85×10−12C2/N⋅m2ε0=8.85×10−12⁢C2/N⋅m2)

120 nm/s

The magnitude of the Poynting vector of a planar electromagnetic wave has an average value of 0.939W/m20.939⁢Wm2. The wave is incident upon a rectangular area, 1.5 m by 2.0 m, at right angles. How much total electromagnetic energy falls on the area during 1.0 minute? (c=3.0×108m/sc=3.0×108⁢ms, μ0=4π×10−7T⋅m/Aμ0=4⁢π×10−7⁢T⋅m/A, ε0=8.85×10−12C2/N⋅m2ε0=8.85×10−12⁢C2/N⋅m2)

170 J

The coil in a 60-Hz ac generator has 125 turns, each having an area of 3.0×10−2m23.0×10−2⁢m2 and is rotated in a uniform 0.12-T magnetic field. What is the peak output voltage of this generator?

170 V

An 800-kHz radio signal is detected at a point 2.7 km distant from a transmitter tower. The electric field amplitude of the signal at that point is 0.36 V/m. Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed. What is the intensity of the radio signal at that point? (c=3.0×108m/sc=3.0×108⁢ms, μ0=4π×10−7T⋅m/Aμ0=4⁢π×10−7⁢T⋅m/A, ε0=8.85×10−12C2/N⋅m2ε0=8.85×10−12⁢C2/N⋅m2)

170µW/m2

A planar electromagnetic wave is propagating in the +x+x direction. At a certain point PP and at a given instant, the electric field of the wave is given by →E=(0.082V/m)ˆjE→=(0.082⁢V/m)⁢j^. What is the Poynting vector at the point PP at that instant? (c=3.0×108m/sc=3.0×108⁢ms, μ0=4π×10−7T⋅m/Aμ0=4⁢π×10−7⁢T⋅m/A, ε0=8.85×10−12C2/N⋅m2ε0=8.85×10−12⁢C2/N⋅m2)

18W/m2ˆi

A rectangular coil having N turns and measuring 15 cm by 25 cm is rotating in a uniform 1.6-T magnetic field with a frequency of 75 Hz. The rotation axis is perpendicular to the direction of the field. If the coil develops a sinusoidal emf of maximum value 56.9 V, what is the value of N?

2

An 800-kHz radio signal is detected at a point 4.5 km distant from a transmitter tower. The electric field amplitude of the signal at that point is 0.63 V/m. Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed. What is the magnetic field amplitude of the signal at that point? (c=3.0×108m/sc=3.0×108⁢ms, μ0=4π×10−7T⋅m/Aμ0=4⁢π×10−7⁢T⋅m/A, ε0=8.85×10−12C2/N⋅m2ε0=8.85×10−12⁢C2/N⋅m2)

2.1 nT

A 45-mH ideal inductor is connected in series with a 60-Ω60-Ω resistor through an ideal 15-V DC power supply and an open switch. If the switch is closed at time t=0st=0⁢s, what is the current 7.0 ms later?

250 mA

How much energy is stored in a room 3.0 m by 4.0 m by 2.4 m due to the earth's magnetic field with a strength of 5.0×10−5T5.0×10−5⁢T? (μ0=4π×10−7T⋅m/A)

29 mJ

The average intensity of the sunlight in Miami, Florida, is 1.04kW/m21.04⁢kW/m2. For surfaces on which the light is all absorbed, what is the average value of the radiation pressure due to this sunlight in Miami? (c=3.0×108m/sc=3.0×108⁢ms, μ0=4π×10−7T⋅m/Aμ0=4⁢π×10−7⁢T⋅m/A, ε0=8.85×10−12C2/N⋅m2ε0=8.85×10−12⁢C2/N⋅m2)

3.47µPa

An inductor has a current I(t)=(0.500A)cos[(275s−1)t]I(t)=(0.500⁢A)cos⁡[(275⁢s−1)t] flowing through it. If the maximum emf across the inductor is equal to 0.500 V, what is the self-inductance of the inductor?

3.64 mH

What is the energy density in the magnetic field 25 cm from a long straight wire carrying a current of 12 A? (μ0=4π×10−7T⋅m/A)

3.7×10−5J/m3

A 7.5×1014Hz7.5×1014⁢Hz laser emits a 7.7-µs7.7-µs pulse, 5.0 mm in diameter, with a beam energy density of 0.51J/m30.51⁢Jm3. What is the amplitude of the electric field of the emitted waves? (c=3.0×108m/sc=3.0×108⁢ms, μ0=4π×10−7T⋅m/Aμ0=4⁢π×10−7⁢T⋅m/A, ε0=8.85×10−12C2/N⋅m2ε0=8.85×10−12⁢C2/N⋅m2)

340 kV/m

If the z-component of the magnetic field of an electromagnetic wave traveling in the +x+x direction through vacuum obeys the equation Bz(x,t)=(1.25µT)cos[(3800m−1)x−1.14×10−12rad/s)t]Bz⁢xt=(1.25⁢µT)⁢cos⁡[(3800⁢m−1)⁢x−1.14×10−12⁢rads)⁢t], what is the largest that the y component of the electric field can be? (c=3.0×108m/s)(c=3.0×108⁢ms).

375N/C

What is the self-inductance of a solenoid 30.0 cm long having 100 turns of wire and a cross-sectional area of 1.00×10−4m21.00×10−4⁢m2? (μ0=4π×10−7T⋅m/A)

4.19µH

A charged capacitor is connected to an ideal inductor. At time t=0t=0, the charge on the capacitor is equal to 6.00µC6.00⁢µC. At time t=2.00mst=2.00⁢ms the charge on the capacitor is zero for the first time. What is the amplitude of the current at that same instant?

4.71 mA

The intensity of solar radiation near the earth is 1.4kW/m21.4⁢kW/m2. What force is exerted by solar radiation impinging normally on a 5.0m25.0⁢m2 perfectly reflecting panel of an artificial satellite orbiting the earth? (c=3.0×108m/sc=3.0×108⁢ms, μ0=4π×10−7T⋅m/Aμ0=4⁢π×10−7⁢T⋅m/A, ε0=8.85×10−12C2/N⋅m2ε0=8.85×10−12⁢C2/N⋅m2)

47µN

A uniform magnetic field is applied perpendicular to the plane of a 60-turn circular coil with a radius of 6.0 cm and a resistance of 0.60Ω0.60⁢Ω. If the magnetic field increases uniformly from 0.20 T to 1.8 T in 0.20 s, what is the magnitude of the emf induced in the coil?

5.4 V

An insulated wire of diameter 1.0 mm and negligible resistance is wrapped tightly around a cylindrical core of radius 5.0 cm and length 30 cm to build a solenoid. What is the energy stored in this solenoid when a current I=0.20AI=0.20⁢A flows through it? (μ0=4π×10−7T⋅m/A)

5.9×10−5J

In an LC circuit containing a 40-mH ideal inductor and a 1.2-mF capacitor, the maximum charge on the capacitor is 45 mC during the oscillations. What is the maximum current through the inductor during the oscillations?

6.5 A

The magnitude of the magnetic field at point PP for a certain electromagnetic wave is 2.12µT2.12⁢µT. What is the magnitude of the electric field for that wave at PP? (c=3.0×108m/s)

636N/C

You are designing a generator to have a maximum emf of 8.0 V. If the generator coil has 200 turns and a cross-sectional area of 0.030m20.030⁢m2, what should be the frequency of the generator in a uniform magnetic field of 0.030 T?

7.1 Hz

Given that the wavelengths of visible light range from 400 nm to 700 nm, what is the highest frequency of visible light? (c=3.0×108m/s)

7.5×10^14Hz

A 96-mH solenoid inductor is wound on a form 0.80 m in length and 0.10 m in diameter. A coil is tightly wound around the solenoid at its center. The coil's resistance is 9.9 ohms. The mutual inductance of the coil and solenoid is 31µH31⁢µH. At a given instant, the current in the solenoid is 540 mA, and is decreasing at the rate of 2.5 A/s. At the given instant, what is the magnitude of the induced current in the coil? (μ0=4π×10−7T⋅m/A)

7.8µA

A charged capacitor is connected to an ideal inductor to form an LC circuit with a frequency of oscillation f=1.6Hzf=1.6⁢Hz. At time t=0t=0 the capacitor is fully charged. At a given instant later the charge on the capacitor is measured to be 3.0µC3.0⁢µC and the current in the circuit is equal to 75µA75⁢µA. What is the maximum charge of the capacitor?

8.0µC

Which of the following statements about inductors are correct? There may be more than one correct choice.

An inductor always resists any change in the current through it.

When an electromagnetic wave falls on a white, perfectly reflecting surface, it exerts a force F on that surface. If the surface is now painted a perfectly absorbing black, what will be the force that the same wave will exert on the surface?

F/2

A circular loop of wire lies in the plane of the paper. An increasing magnetic field points out of the paper. What is the direction of the induced current in the loop?

clockwise

The energy per unit volume in an electromagnetic wave is

equally divided between the electric and magnetic fields.

If the magnetic field of an electromagnetic wave is in the +x+x direction and the electric field of the wave is in the +y+y direction, the wave is traveling in the

−z−z direction