Magnetic field and magnetic forces | Practice Problems, Examples & Solutions

Magnetism

21st Century Astronomy

The magnetic field of the Milky Way has been detected by
a. synchrotron radiation from cosmic rays.
b. direct observation of the field.
c. its interaction with Earth's magnetic field.
d. studying molecular clouds.

The Milky Way—A Normal Spiral Galaxy

00:31

21st Century Astronomy

Sunspots, flares, prominences, and coronal mass ejections are all caused by
a. magnetic activity on the Sun.
b. electrical activity on the Sun.
c. the interaction of the Sun's magnetic field and the interstellar medium.
d. the interaction of the solar wind and Earth's magnetic field.
e. the interaction of the solar wind and the Sun's magnetic field.

Our Star—The Sun

04:23

Organic Chemistry

a. Calculate the magnetic field (in tesla) required to flip an $^{1}$ H nucleus in an NMR spectrometer that operates at $360 \mathrm{MHz}$
b. What strength magnetic field is required when a $500-\mathrm{MHz}$ instrument is used for $^{1} \mathrm{H}$ NMR?

NMR Spectroscopy

Magnetic Field Lines and Magnetic Flux

490 Practice Problems

00:49

21st Century Astronomy

Scientists know the history of Earth's magnetic field because
a. the magnetic field hasn't changed since Earth formed.
b. they see today's changes and project backward in time.
c. the magnetic field becomes frozen into rocks, and plate tectonics spreads those rocks apart.
d. they compare the magnetic fields on other planets to Earth's.

The Terrestrial Planets and Earth's Moon

00:29

21st Century Astronomy

The layers in a high-mass star occur roughly in order of
a. atomic number.
b. decay rate.
c. magnetic field strength.
d. spin state.

Evolution of High-Mass Stars

00:44

21st Century Astronomy

Coronal mass ejections
a. carry away 1 percent of the mass of the Sun each year.
b. are caused by breaking magnetic fields.
c. are always emitted in the direction of Earth.
d. are unimportant to life on Earth.

Our Star—The Sun

Motion of Charged Particles in a Magnetic Field

67 Practice Problems

03:08

Principles of Physics a Calculus Based Text

A proton moves through a region containing a uniform electric field given by $\overrightarrow{\mathbf{E}}=50.0 \hat{\mathbf{j}} \mathrm{V} / \mathrm{m}$ and a uniform magnetic field $\overrightarrow{\mathbf{B}}=(0.200 \hat{\mathbf{i}}+0.300 \hat{\mathbf{j}}+0.400 \hat{\mathbf{k}})$ T. Determine the acceleration of the proton when it has a velocity $\overrightarrow{\mathbf{v}}=200 \hat{\mathbf{i}} \mathrm{m} / \mathrm{s}$.

Electromagnetic Waves

04:47

Principles of Physics a Calculus Based Text

A proton moves with a velocity of $\overrightarrow{\mathbf{v}}=(2 \hat{\mathbf{i}}-4 \hat{\mathbf{j}}+\hat{\mathbf{k}}) \mathrm{m} / \mathrm{s}$ in a region in which the magnetic field is $\overrightarrow{\mathbf{B}}=(\hat{\mathbf{i}}-\mathbf{2} \hat{\mathbf{j}}-\hat{\mathbf{k}})$ T. What is the magnitude of the magnetic force this particle experiences?

Magnetic Forces and Magnetic Fields

02:45

Principles of Physics a Calculus Based Text

A proton travels with a speed of $3.00 \times 10^{6} \mathrm{m} / \mathrm{s}$ at an angle of $37.0^{\circ}$ with the direction of a magnetic field of $0.300 \mathrm{T}$ in the $+y$ direction. What are (a) the magnitude of the magnetic force on the proton and (b) its acceleration?

Magnetic Forces and Magnetic Fields

Magnetic Force on a Current-Carrying Conductor

96 Practice Problems

01:23

University Physics

Discuss the factors determining the induced emf in a closed loop of wire.

Electromagnetic Induction

01:26

University Physics

A magnetic field exerts a force on the moving electrons in a current carrying wire. What exerts the force on a wire?

Magnetic Forces and Fields

01:18

University Physics

Considering the magnetic force law, are the velocity and magnetic field always perpendicular? Are the force and velocity always perpendicular? What about the force and magnetic field?

Magnetic Forces and Fields

Force and Torque on a Current Loop

15 Practice Problems

00:53

University Physics

In which situation shown below will the electromagnetic wave be more successful in inducing a current in the loop? Explain.

Electromagnetic Waves

02:32

University Physics

How would changing the radius of loop $D$ shown below affect its emf, assuming $C$ and $D$ are much closer together compared to their radii?

Electromagnetic Induction

02:43

Physics for Scientists and Engineers with Modern Physics

The current in a loop circuit that has a resistance of $R_{1}$ is 2.00 A. The current is reduced to 1.60 $\mathrm{A}$ when an additional resistor $R_{2}=3.00 \Omega$ is added in series with $R_{1}$ . What is the value of $R_{1} ?$

Direct-Current Circuits

The Direct-Current Motor

1 Practice Problems

01:00

University Physics

Will a transformer work if the input is a dc voltage?

Alternating-Current Circuits

The Hall Effect

5 Practice Problems

00:51

University Physics

The Hall effect is demonstrated in the laboratory. A thin rectangular strip of semiconductor with width $5 \mathrm{cm}$ and cross-sectional area $2 \mathrm{mm}^{2}$ is attached to a battery and immersed in a field perpendicular to its surface. The Hall voltage reads $12.5 \mathrm{V}$ and the measured drift velocity is 50 m/s. What is the magnetic field?

Condensed Matter Physics

00:57

University Physics

An experiment is performed to demonstrate the Hall effect. A thin rectangular strip of semiconductor with width
$10 \mathrm{cm}$ and length $30 \mathrm{cm}$ is attached to a battery and immersed in a $1.50-T$ field perpendicular to its surface. This produced a Hall voltage of 12 V. What is the drift velocity of the charge carriers?

Condensed Matter Physics

01:06

Physics

A strip of copper carries current in the $+x$ -direction. There is an external magnctic field directed out of the page. What is the direction of the Hall electric field?

Magnetic Forces and Fields

The Biot–Savart Law

5 Practice Problems

01:17

University Physics

For calculating magnetic fields, what are the advantages and disadvantages of the Biot-Savart law?

Sources of Magnetic Fields

00:47

Essential University Physics

The Biot-Savart law shows that the magnetic field of a current element decreases as $1 / r^{2} .$ Could you put together a complete circuit whose field exhibits this decrease? Why or why not?

Magnetism: Force and Field

01:31

Essential University Physics

The Biot-Savart law shows that the magnetic field of a current element decreases as $1 / r^{2} .$ Could you put together a complete circuit whose field exhibits this decrease? Why or why not?

Magnetism: Force and Field