To a current-carrying conductor $5\,\text{A}$ and length $40\,\text{sm}$ maximum force acting in a magnetic field $5\,\text{mN}$. What is the magnetic field induction?

B = 2{,}5\cdot 10^{-3}\,\text{Tl}

What should be the angle between the conductor length $20\,\text{sm}$ and the magnetic induction vector $B=4\,\text{mTl}$, so that with current $15\,\text{A}$ the strength was: a) $6\,\text{mN}$, b) $18\,\text{mN}$?

\alpha_1 = 30^{\circ}; \alpha_2\ \text{not exists}

The electron moves at a speed $2\cdot10^{7}\,\text{m/s}$ perpendicular to the field with induction $40\,\text{mTl}$. Determine the Lorentz force, the radius of the trajectory and the period of revolution.

F_{\text{l}} = 1{,}28\cdot 10^{-13}\,\text{N}; R = 0{,}0028\,\text{m}; T = 8{,}9\cdot 10^{-10}\,\text{s}

Homogeneous electric and magnetic fields are mutually perpendicular: $E=0{,}5\,\text{kV/m}$, $B=0{,}001\,\text{Tl}$. At what speed and in what direction should the electron move uniformly?

v = 5\cdot 10^{5}\,\tfrac{\text{m}}{\text{s}}

In a coil with inductance $0{,}5\,\text{Gn}$ current flows $8\,\text{A}$. What is the energy of the magnetic field? How to change the current so that the energy increases in $9$ once?

W_{\text{m}} = 16\,\text{J}; I' = 24\,\text{A}

An electron flies perpendicularly into a magnetic field with a speed $5\,\text{Mm/s}$ and moves in a circle with radius $1{,}1\,\text{sm}$. Determine the field induction and revolution period.

B = 2{,}6\cdot 10^{-3}\,\text{Tl}; T = 1{,}38\cdot 10^{-8}\,\text{s}

11TH GRADE PRACTICE

Physics Problems: Magnetism, Grade 11

Magnetic field forces and induction.

11 problems across 2 sub-topics

Practise in the interactive mode

Here the conditions and analysis of the solution can be read without an account. In the simulator, you need to collect the same analyzes yourself: “Given,” formulas, order of steps and answer.

Problem statements

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11 problems

Position in this set: 1 from 11

Problem #1

Magnetism: magnetic field forces

To a current-carrying conductor and length maximum force acting in a magnetic field . What is the magnetic field induction?

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Given

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The force is maximum at an angle of 90°, so the sine is equal to one.

Answer

Position in this set: 2 from 11

Problem #2

Magnetism: magnetic field forces

What should be the angle between the conductor length and the magnetic induction vector , so that with current the strength was: a) , b) ?

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Given

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Sine cannot be greater than one: the maximum force under these conditions is 12 mN, so 18 mN is unattainable.

Answer

Position in this set: 3 from 11

Problem #3

Magnetism: magnetic field forces

The electron moves at a speed perpendicular to the field with induction . Determine the Lorentz force, the radius of the trajectory and the period of revolution.

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Given

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The Lorentz force plays the role of a centripetal force.

Answer

Position in this set: 4 from 11

Problem #4

Magnetism: magnetic field forces

Homogeneous electric and magnetic fields are mutually perpendicular: , . At what speed and in what direction should the electron move uniformly?

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Given

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The movement is uniform when the Lorentz force balances the electric force; We neglect the gravity force of the electron.
The electron must fly perpendicular to the induction vector.

Answer

Position in this set: 5 from 11

Problem #5

Magnetism: magnetic field forces

A proton flew into a magnetic field at a speed perpendicular to the induction vector. Determine the orbital radius and orbital period at .

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The period does not depend on the particle speed.

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Position in this set: 6 from 11

Problem #6

Magnetism: magnetic field forces

In a magnetic field with induction a horizontal conductor of length and mass . The conductor is perpendicular to the induction vector. Determine the current.

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Given

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Equilibrium: Ampere's force balances the force of gravity.

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Position in this set: 7 from 11

Problem #7

Magnetism: electromagnetic induction

Coil diameter has turns and is in a magnetic field parallel to the axis of the coil. What is the EMF if induction changed from up to ?

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The field is parallel to the coil axis, so the cosine is equal to one.

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Position in this set: 8 from 11

Problem #8

Magnetism: electromagnetic induction

When the current in the coil changes by inductance for self-induced emf occurred . How much has the current changed?

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Answer

Position in this set: 9 from 11

Problem #9

Magnetism: electromagnetic induction

In a coil with inductance current flows . What is the energy of the magnetic field? How to change the current so that the energy increases in once?

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Energy grows as the square of the current, so to increase by 9 times the current must be tripled.

Answer

Position in this set: 10 from 11

Problem #10

Magnetism: electromagnetic induction

Closed resistance conductor is in a magnetic field. What charge will pass through the conductor when the magnetic flux changes by ?

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Given

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The induction current is determined by Faraday's law and Ohm's law.
Time is reduced: charge depends only on changes in flux and resistance.

Answer

Position in this set: 11 from 11

Problem #11

Magnetism: magnetic field forces

An electron flies perpendicularly into a magnetic field with a speed and moves in a circle with radius . Determine the field induction and revolution period.

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Given

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Answer

The theory behind these problems

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Magnetic field and forcesInduction, Ampere force, Lorentz force and charge motion.Magnetic flux and inductionFlux, electromagnetic induction, self-induction and field energy.

Formulas by topic

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InductanceL · Gn Magnetic inductionB · Tl Magnetic fluxΦ · Wb Velocityv · m/s EnergyE, W · J