Magnetic Fields Flashcards

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1
Q

What is another word for field lines?

A

Lines of Flux

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2
Q

In what direction do field lines go?

A

From the north pole to the south pole

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3
Q

How can a magnetic field be induced in a wire?

A

By moving current through it

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4
Q

What is conventional current?

A

Current that goes from the positive terminal to the negative

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5
Q

How can you find the direction of the magnetic field around a current-carrying wire?

A

The right-hand rule.
Thump is current
Fingers travel in the direction of the field

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6
Q

What happens if you place a current-carrying wire in a magnetic field?

A

It will experience a force that’s perpendicular to the magnetic field and the current

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7
Q

Flemmings left-hand rule?

A

First finger is Field (index)
seCond finger Current (middle)
Thumb shows you the direction of the force

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8
Q

What happens if the current is parallel to the field lines?

A

No force

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9
Q

How to determine the force on a current-carrying wire in a magnetic field?

A

F = BILsinθ
B is flux density
I is current
L is length of the wire

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10
Q

What happens if you put a charged particle in a magnetic field?

A

A force acts upon it, this is the reason that the force acts on a wire with a current moving through it

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11
Q

How to determine the force that acts on a particle in a magnetic field?

A

F = Bqvsinθ
B is flux density
q is charge of particle
v is velocity of particle

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12
Q

What is magnetic flux?

A

Φ = BA
Magnetic Flux = Flux Density * Area
It’s the strength of the field as a collective (total field)

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13
Q

What happens if there is relative motion between a conducting rod and a magnetic field?

A

The electrons in the rod will experience a force, causing them to accumulate at one end of the rod
Causing p.d (emf) to be induced

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14
Q

How to induce am e.m.f in a solenoid?

A

Moving the coil away from the poles of the magnet
Moving the magnet towards or away from the coil
Passing a p.d through the coil

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15
Q

What does the size of the emf depend on?

A

The magnetic flux passing through the coil
the number of turns in the coil

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16
Q

What is the flux linkage?

A

NΦ = NBA
It is the product of the number of turns and the flux

17
Q

The Law relating the fluxlinkage, emf and time taken?

A

Faraday’s law
emf = change in flux linkage / time taken or
ϵ = dNΦ / dt

18
Q

What law helps to deduce the direction of the induced emf?

A

Lenz’s Law The induced emf is always in the opposite direction of the of the change that caused it.

19
Q

RMS p.d?

A

V / sqrt(2)

20
Q

Why would a copper disk rotate in the same direction as a plastic disk filled with magnets

A

Lenz’s law
Copper disk rotates on Same direction to reduce change in flux as it acts to oppose the change that produces it