5) Magnetic Fields Flashcards
(9 cards)
State what is meant by root mean square voltage.
the square root of the mean of the squares of all the values of the voltage in one cycle.
State and explain the effect on the oscilloscope trace if the time base is switched off.
- vertical line is formed of length equal to twice the peak voltage.
- because trace no longer moves horizontally.
State two situations in which a charged particle will experience no magnetic force when placed in a magnetic field.
- when charged particle is at rest.
- when charged particle moves parallel to magnetic field.
Explain what is meant by the term magnetic flux linkage. State its unit.
- product of flux and number of turns.
- Wb.
State Lenz’s law.
direction of induced emf opposes change of magnetic flux that produces it.
Define the tesla.
the strength of the magnetic field density that produces a force of 1 newton in a wire of length 1m with 1 ampere flowing perpendicular to the field.
Outline the essential features of a step-down transformer when in operation.
- primary coil with more turns than secondary coil.
- wound around a core.
The equation F = BQv may be used to calculate magnetic forces. State the condition under which this equation applies.
B must be at right angles to v.
Explain how a step-down transformer differs in construction from a step-up transformer.
primary coil must have more turns than secondary.
