Earth's Magnetic Field

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Questions and Answers

What is the force on a wire carrying a current in a uniform magnetic field proportional to?

The magnitude of the magnetic flux density

The distance travelled by the charged particles

The velocity of the charged particles

The current in the wire (correct)

What is the direction of the velocity of negatively charged particles with respect to the current?

In the same direction as the current

Perpendicular to the current

In the opposite direction to the current (correct)

Parallel to the magnetic field

What is the unit of the magnetic flux density?

Newton

Tesla (correct)

Ampere

Weber

What is the formula for the force on a charged particle in a uniform magnetic field?

F = BLv Signup and view all the answers

What is the physical quantity that can be determined from the gradient of the I-m graph?

Magnetic flux density Signup and view all the answers

What is the relationship between the velocity of charged particles and the current in a wire?

The velocity is proportional to the current Signup and view all the answers

What is the purpose of Fleming's left-hand rule in this context?

To determine the direction of the force on a charged particle Signup and view all the answers

What is the formula for the mean speed of charged particles?

v = d/t Signup and view all the answers

What is the direction of the magnetic field lines in a bar magnet?

From the north pole to the south pole Signup and view all the answers

Why does a compass point approximately to the geographic north?

Because of the alignment of the compass with the Earth's magnetic field Signup and view all the answers

What is the purpose of the Earth's magnetic field?

To protect us from the solar wind Signup and view all the answers

What is the term for the density of magnetic field lines?

Magnetic flux density Signup and view all the answers

What is the shape of the container used in nuclear fusion to generate a uniform magnetic field?

Toroidal (doughnut-shaped) Signup and view all the answers

What is the effect of like poles in a magnet?

Repulsion Signup and view all the answers

What is the term for the interaction between the solar wind's magnetic field and the Earth's magnetic field?

Magnetic deflection Signup and view all the answers

What is the purpose of the uniform magnetic field in nuclear fusion?

To force high energy protons into close proximity Signup and view all the answers

What is the force due to the electric field given by?

𝐹𝐹 = 𝐸𝐸𝑠𝑠 𝑄𝑄 Signup and view all the answers

What is the velocity of the particles that travel in a straight line?

𝐸𝐸𝑠𝑠 / 𝐵𝐵𝑠𝑠 Signup and view all the answers

What is the purpose of velocity selection in mass spectrometry?

To determine the molecular formula of an unknown substance Signup and view all the answers

What is the magnetic flux density, 𝐵𝐵, defined as?

The magnetic flux per unit area Signup and view all the answers

What is the magnetic flux, 𝜙𝜙, through an area, 𝐴𝐴, defined as?

The product of the magnetic flux density and the area perpendicular to the lines of flux Signup and view all the answers

What is the angle between the area and the magnetic flux lines denoted by?

𝜃𝜃 Signup and view all the answers

What is the purpose of the velocity selector in mass spectrometry?

To ensure that a small proportion of ions emerge with equal velocities Signup and view all the answers

What is the area, 𝐴𝐴, in the equation for magnetic flux?

The cross-sectional area of the coil Signup and view all the answers

What happens to the wire when it is moved out of a magnetic field?

It is pulled back into the field by the magnet Signup and view all the answers

What determines the direction of the current in a solenoid when a bar magnet is pushed into it?

Lenz's law and the right-hand grip rule Signup and view all the answers

What is the purpose of a search coil?

To measure the strength of a magnetic field Signup and view all the answers

What happens to the magnetic flux when a search coil is withdrawn from a magnetic field?

It decreases Signup and view all the answers

What is the relationship between the induced current and the rate of change of flux linkage?

The induced current is directly proportional to the rate of change of flux linkage Signup and view all the answers

How is the magnetic field strength calculated using a search coil?

By measuring the maximum current induced in the search coil and using a calibration constant Signup and view all the answers

What is the purpose of calibrating a search coil?

To determine the constant of proportionality between the induced current and the magnetic field strength Signup and view all the answers

What is required to evaluate the magnetic flux?

The area and number of turns of the search coil Signup and view all the answers

What is the primary function of the iron core in a transformer?

To ensure maximum energy transfer between coils Signup and view all the answers

What is the effect on the voltage of the alternating current source when the transformer is step-up?

The voltage is increased Signup and view all the answers

What is the relationship between the e.m.f. in the primary coil and the change in magnetic flux?

The e.m.f. is directly proportional to the change in magnetic flux Signup and view all the answers

What is the condition for a transformer to be step-down?

Ns < Np Signup and view all the answers

What is the purpose of the primary coil in a transformer?

To transmit energy to the secondary coil Signup and view all the answers

What is the direction of the current induced in the secondary coil?

In the opposite direction to the primary coil Signup and view all the answers

What is the effect of increasing the number of turns in the secondary coil?

The voltage in the secondary coil increases Signup and view all the answers

What is the relationship between the number of turns in the primary and secondary coils?

Ns is directly proportional to Np Signup and view all the answers

Study Notes

Magnetic Field of the Earth

The Earth's magnetic field has a north and south pole, but the magnetic north is in the southern hemisphere and vice versa.
The Earth's magnetic field protects us from the solar wind (high-energy charged particles from the sun).
The interaction between the solar wind's magnetic field and the Earth's magnetic field causes harmful particles to be deflected and concentrated at the poles, resulting in the aurora borealis and aurora australis.

Magnetic Field Lines

Magnetic fields can be represented by field lines or lines of magnetic flux, which point from the north pole to the south pole.
The density of these lines of flux represents the strength of the magnetic field.
The strength of the magnetic field can be measured by the density of field lines.

Magnetic Fields and Charged Particles

Like poles repel and opposite poles attract.
In a uniform magnetic field, charged particles can be forced into close proximity and fused (in nuclear fusion).
The force on a charged particle in a uniform magnetic field can be calculated using the formula F = BQv, where F is the force, B is the magnetic flux density, Q is the charge, and v is the velocity.

Motion of a Charged Particle in a Uniform Magnetic Field

The force on a charged particle in a uniform magnetic field can be calculated using the formula F = BQv.
The velocity of the particle can be calculated using the formula v = E/B, where E is the electric field strength.
Particles travelling at a certain velocity will travel in a straight line, while particles travelling at any other velocity will curve and collide with the plates.

Mass Spectrometry

Velocity selection is used in mass spectrometry to determine the molecular formula of an unknown substance.
Molecules are broken down into their constituent atoms, ionized, and accelerated through a large potential difference.
A velocity selector is used to select particles with equal velocities, and a uniform magnetic field is used to deflect the particles based on their mass-to-charge ratio.

Magnetic Flux Linkage

The magnetic flux density, B, is the magnetic flux per unit area.
The magnetic flux, φ, through an area, A, is defined as the product of the magnetic flux density and the area perpendicular to the lines of flux: φ = BAcosθ.

Experimental Techniques for Investigating Magnetic Flux

A search coil is a flat coil of insulated wire connected to a galvanometer.
The search coil is used to determine the strength of a magnetic field from the current induced in the coil when it is withdrawn.
The coil is calibrated by measuring the maximum current induced in the coil when it is quickly withdrawn from a known magnetic field.

Transformers

Transformers raise or lower the voltage of alternating current sources using electromagnetic induction.
The primary coil induces a varying magnetic flux in the iron core, which induces a current in the secondary coil.
The ratio of the number of turns in the primary and secondary coils determines whether the transformer is step-up or step-down.

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Description

This quiz explores the basics of Earth's magnetic field, its poles, and its importance in protecting us from the solar wind.