magnetism

[Bestie]

how does a current cause a magnetic field?

thank you

[Jacyan]

This will never be asked in VCE. To answer this, I believe you need to understand special relativity.

[Bestie]

oh ok yup thank you

another question?
Describe and discuss the force of Earth’s magnetic
field on a horizontal section of a power line that
runs in an east–west direction.

thankyou

[Bestie]

im sorry... but can someone also help me with this question?
Can a magnetic field move a stationary electron? Why? Explain your answer.

thank you

[Jacyan]

oh ok yup thank you

another question?
Describe and discuss the force of Earth’s magnetic
field on a horizontal section of a power line that
runs in an east–west direction.

thankyou

With any question related to force and magnetic fields, the right hand slap rule is a good place to start. Remember that the magnetic north pole of the earth is actually at the geographic south pole of the earth (and hence the magnetic field is from the earth's geographic south pole to the north pole). Since the horizontal section of the power line runs in an east-west direction, we know the direction of the current. Therefore, just apply the right hand slap rule to get the direction of the force.

im sorry... but can someone also help me with this question?
Can a magnetic field move a stationary electron? Why? Explain your answer.

thank you

If I am understanding this question right, yes, technically a magnetic field can move a stationary electron due to electromagnetic induction. For example, in a generator, to generate electricity, a coil is rotated (by mechanical means) in an magnetic field. Rotation of coil in a magnetic field causes a change of flux being induced in the coil. A change of flux produces an emf (and hence a current).

[Bestie]

thank you so much Jacyan

if possible can you help me here too:
22. (a) A beam of electrons is directed at right angles
to a wire carrying a conventional current from
left to right. What happens to the electrons?
(b) A beam of electrons is directed parallel to the
same wire with the conventional current travelling
in the same

please and thank you

[lzxnl]

You've made a misunderstanding there. For your rotating coil, the charges in the coil are already moving. They're rotating. What actually happens is that the changing magnetic flux produces an electric field, which only THEN acts on the charges. The magnetic field itself doesn't actually interact with the charges.

By the Lorentz force formula, F = qv cross B, if v=0, F=0. Magnetic fields only interact with moving charges.

However, the distinction between an electric and magnetic field is a fine one because special relativity would then go on to say they're the same thing. They ARE similar to some extent. Imagine you have an electron moving in a straight line at constant speed. Let's say you have two observers, observer A who is in the lab frame and observer B who is moving with the electron. Now put this electron in a 'magnetic field'. The observers aren't accelerating with respect to one another, so they must measure the same forces. Observer A sees a moving electron acted upon by a magnetic field, as expected. Observer B must therefore also measure some form of disturbance to the electron's path. However, observer B is moving WITH the electron; he/she sees the electron as stationary. Therefore, observer B can't be seeing a magnetic force acting on the electron. As a result, observer B sees an electric force acting on the electron.

Confusing? This is why VCE physics only scrapes the surface of things.