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21 Cards in this Set

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Magnetic Fields can be formed around?

A magnetic field is formed around a current carrying wire. (Use Right Hand Grip Rule)

What do you use Fleming's Left Hand Rule for?

A current carrying wire experiences a force in a magnetic field. Use Fleming’s Left Hand Rule.The magnitude of the force is : F = B I l

What does a moving charge in a magnetic field feel? And what is this the same as?

A charge moving in a magnetic field experiences a force. A moving charge is the same as a current. Use Fleming’s Left Hand Rule. The magnitude of the force is given by: F = B q v

What do cyclotrons use magnetic fields for?

Cyclotrons use magnetic fields to keep charged particles in circular orbits

When a wire moves in a magnetic field what happens?

A current is induced in a wire if it moves in a magnetic field. (Use Fleming’s Right Hand Rule)

What is Faraday's law?

The induced e.m.f. is directly proportional to the rate of change of magneticflux linkage

What is Lenz's law?

The direction of the induced e.m.f. is such as to oppose the change that inducesit

What do step-up transformers do?

Step-up transformers increase the voltage

Why is a high voltage used in the national grid?

High voltage is used in the National Grid to reduce power loss to resistance of cables

What causes inefficiency?

Causes of inefficiency:o Eddy currentso Resistance in coilso Not all of magnetic flux though coil one passes through coil two

What can magnetic fields be represented by?

Magnetic fields can be represented by field lines, field lines go from north to south and the closer together the lines, the stronger the field

What is the difference in field lines of looping into a coil or solenoid (lots of coils)?

If you loop a wire into a coil, the field line is doughnut shaped.
If you have lots of coils, it forms a field like a bar magnet

What happens if you put a current-carrying wire into an external magnetic field?

If you put a current carrying wire into an external magnetic field, the field around the wire and the magnetic field interact. The magnetic field lines contract to form a 'stretched catapult' effect, where the flux lines are closer together

What is magnetic field strength defined as for a current-carrying wire in a magnetic field?

The force on one metre of wire carrying a current of one amp at right angles to the magnetic field

What is magnetic field strength/flux density measured in?

Magnetic field strength/flux density is measured in Tesla's (T)

What path do charged particles in a magnetic field follow?

Charged particles in a magnetic field follow a circular path - you can identify different particles by how they are deflected as you can gain information on their charge and mass (due to the path they take)

What is magnetic flux density?

Magnetic flux density a measure of strength of a magnetic field per unit area

How does a conducting rod induce an EMF in a magnetic field?

When moving through the magnetic field, the electrons within it will experience a force, meaning they will accumulate at one side of the rod. This will induce an EMF across the ends of the rod, if attached to a circuit this can be used to induce a current - electromagnetic induction

Flux cutting always induces an ____ but will only induce a ____ if the circuit is complete?

Flux cutting always induces an EMF but will only induce a CURRENT if the circuit is complete

What is flux linking?

Flux linking is when an EMF is induced by changing the magnitude or direction of the magnetic flux

What does the area under a graph of EMF against time give?

The area under the graph of EMF against time gives the flux change